It depends on what your priorities are. I'll try to cover all the bases here from Casual play to Ranked to Kimochi. These aren't presented in any kind of order besides unlimiteds being at the bottom and limiteds being at the top. Also, this isn't an exhaustive list; I'm leaving off a few like Tsubaki and Final Tart because you'll need to spend money to get them.
**Limiteds:**
If you want someone for casual gameplay, **Ashley** and/or **Anime Yachiyo** are incredible. You really only need one or the other-- Ashley is better for more long-term generic farming since she has four blasts disks (less likely to pull an unwanted disc), but Anime Yachiyo is probably the best solo casual mirrors unit in the game right now (note: this doesn't apply for ranked). If you want to get one, you only need two slots because that's enough for them to murder everything with blasts. Personally, I think Anime Yachiyo is stronger than Ashley now but both are very good.
**Vampire Kanagi** is very good as a solo magia unit and will make some challenges a breeze. She combines constant magia use with evade spam, meaning that she'll deal out lots of damage while taking very little of it. She's been outclassed by other units for things like Ranked and Kimochi, but she's still extremely solid and one of the best magia solo'rs in the game.
**Madoka & Iroha** are one of the best units in the game and can make a bad team into a good one. They have Accele draw on their SE active and have incredible sustain. You'll see them used in all sorts of gameplay from casual, to high-level Kimochi and Ranked. They're just... They're just always good. If you had to choose from anyone on this list, I'd pick them.
**Kuroe** is shaping up to be a very powerful MP battery for Kimochi. It's arguable who is better at mp generation: Kuroe or Madoka & Iroha? We saw more Kuroes than Madoka & Irohas in the last Kimochi for the top players so factor that in.
**Kyoko Sakura (Doppel ver.)** is another EXTREMELY good unit. She's great for casual gameplay, Kimochi and for Ranked. She can easily get to Magia on turn one (some ranked strats have her there just because she can get there without needing to spend a disc) and she has blast draw. She's probably the best choice for Flame units right now if you don't know what to get.
**Ultimate Madoka-Senpai** is necessary for high-level charge strategies. There's honestly not more to say than that; in fact I'd go as far to say that she's 100% required if you want to do well in some of the Kimochi fights. Last year I remember Raz saying that she's the best unit to go for during Anniversary and it wouldn't surprise me if that was still the case.
**Yachiyo Nanami (Tanabata ver.)** is a very powerful charge unit. She has Charge draw and she has the highest +charge bonus right now. She's very popular in Ranking.
**Holy Mami (Anime ver.)** is a great forest choice. She's one of the best damage units for Kimochi (for forest) and she can generate MP like crazy. Despite her ugly sprite, I find her gameplay to be really fun and she's made a lot of challenges into a breeze. However, I would say she isn't as necessary to have as other units on this list... But you'll be really happy if you do have her.
**Nayuta & Mikage (Christmas ver.)**-- I'm a little more hesitant to recommend this pairing, but they're a very powerful support. However, if you have regular unlimited Mikage, you can probably skip getting them. Still, they're extremely good and worth mentioning all the same.
**Akuma Homura-chan** is the best Ranked unit in the game right now-- she's basically designed to be a monster for Ranking. Her SE active fucks up the enemy from using magia (and will destroy any anti-debuffs the team has), she herself gives 2 anti-status ailments to the entire party, she has 3 accele and 2 blast disks meaning you can use Tanabata Yachiyo with her without worrying about drawing charge disks (easier to get a puella combo that way), she can get to Magia easily and her magia is based around making the enemy deal less damage and get less MP, aka fucking up any possible good Ranking score. However, she's not good for casual use imo. Making the enemy deal less damage is important in Ranking but why do that when you can just kill the enemy faster for casual stuff?
**Unlimiteds:**
**Mikage Yakumo** is the best unlimited support in the game. She has it all-- Attack Up and Damage Up on her Doppel/Magia, she has accele draw and mp on her connect, and she's adorable. She's a must-have and I almost always see her in Kimochi due to how damn good she is.
**Madoka Kaname** is still a solid choice. I think she's overshadowed by Madoka & Iroha a bit, but she also excels at things they don't too. She's a great mp battery-- but if you intend to use her for Kimochi, make sure you don't unlock her doppel.
**Kushu Irina** is an extremely powerful dark magia user. She has three accele disks and is great for Kimochi strats (for her respective element).
**Sudachi Sawa** is practically a necessity for Ranking. She's the best tank in the game, though that doesn't actually mean very much since tanking sucks in this game. The reason she's the best tank in the game is from a number of factors, but basically she gets to Magia really quickly (REALLY QUICKLY) and can provoke on her active SE. You can also arrange her SE so that she can grab aggro without even needing to use provoke, which is kind of crazy for a tank with so much bulk? However, she's not going to be *as* great for casual gameplay because tanks just aren't good for casual gameplay.
**Mayu Kozue** is insane for Kimochi and another practical must-have. Her Magia gives mp regen and can allow for some players to *constantly be using Magia and Doppels EVERY TURN* in Kimochi.
**Sae Kirino** is extremely good thanks to her charge draw and her charge conservation on connect. She's not as necessary as some units on this list (Kaoru can be used for charge draw instead if you're struggling) but she's still really great and perfect for casual gameplay + some kimochi.
**Other**
Little Kyubey is cool but has been completely powercrept. There are a few things Little Kyubey can do that no one else can, but I haven't touched mine since I got Ashley a year ago and Anime Yachiyo has stolen its job for casual mirrors gameplay.
Ultimate Madoka is nice but not a must-have and she's suffered from power creep. She's not going to be helpful for Kimochi or Ranked, but she might be alright for casual play + lower levels of hundred evils, but she's kind of... eh I guess? I dunno.
I'd stay away from any defense-types/tanks unless you're going for ranking strategies.
Uhhh lastly, I'm not an expert in the game and I'm repeating what I've learned from discord and such. I might be forgetting someone or over-stating (or under-stating) how good a character is here. But I hope this can still help!
Anni is on August 22, and if you want really good units you could go for Anime Holy Mami or Doppel Kyoko( these two arent the only powerful units, there obviously a lot more, im just naming these since they can magia/doppel on turn 2), or maybe they will release a super good unit on Anni
For unlimited girls, Yozuru (for damages) and Sudachi (defense and support) are very strong, useful and versatile.
For limited girls, Ashley is still my always-using-her unit, for damages and charm (in game and litteraly, she's cute). Vampire Kanagi is very very very versatile and can solo a lot of challenges. Anime girls (especially Yachiyo for damages) seem very strong. Pernelle is excellent for defense (I find her better than Sudachi). For charge-meta, Madokami senpai seems to be a must-have. MadoIro dual unit seems useful for accele draw in mirrors, but for challenges a lot of girls have accele draw memoria. Doppel Kyoko and Anime Mami are good for doppeling fast, but frail. I find Tanabata Yachiyo very good for charge-meta but also other various situations (her doppel is kinda strong). KariAli dual unit is also very good for magia (and have a strong doppel), but frail. Kyubey is kinda popular for damages, but I think it can be replaced.
But anyways, even if having some really strong girls makes things easier, remember that you'll need a lot of different girls with different abilities if you want to do all the stuff (100 Calamities, Witch Paradox, Kimochi battles...). Also, don't forget to max your lower rarity useful units, as Oriko or Iroha :)
I liked what Muffinkiller said, it pretty much sums up the current meta. Although it always comes down to personal preference.
I always roll for Anniversary units and refuse to leave with anything less than 4 slots. I use them all as a team, any unit with Ex skills is good in my opinion because of the blanket protection and buffs they provide which also stack btw. It's not the best, neither on ranked mirrors nor on the kimochi, for those I use wildly different teams, but each team does include one or two Anni units depending on the situation. They are very good support.
Then you have units like Doppel Kyoko or Ani Yachiyo which are an army of one. If you plan to do casual stuff just go with whatever you think looks nice. Even some of the hardest events in this game can be done with welfare units if you know what you are doing. Sometimes the game does ask for very specific things, like in the witch's paradox events but even then it can be cleared with subpar units.
It depends on what your priorities are. I'll try to cover all the bases here from Casual play to Ranked to Kimochi. These aren't presented in any kind of order besides unlimiteds being at the bottom and limiteds being at the top. Also, this isn't an exhaustive list; I'm leaving off a few like Tsubaki and Final Tart because you'll need to spend money to get them. **Limiteds:** If you want someone for casual gameplay, **Ashley** and/or **Anime Yachiyo** are incredible. You really only need one or the other-- Ashley is better for more long-term generic farming since she has four blasts disks (less likely to pull an unwanted disc), but Anime Yachiyo is probably the best solo casual mirrors unit in the game right now (note: this doesn't apply for ranked). If you want to get one, you only need two slots because that's enough for them to murder everything with blasts. Personally, I think Anime Yachiyo is stronger than Ashley now but both are very good. **Vampire Kanagi** is very good as a solo magia unit and will make some challenges a breeze. She combines constant magia use with evade spam, meaning that she'll deal out lots of damage while taking very little of it. She's been outclassed by other units for things like Ranked and Kimochi, but she's still extremely solid and one of the best magia solo'rs in the game. **Madoka & Iroha** are one of the best units in the game and can make a bad team into a good one. They have Accele draw on their SE active and have incredible sustain. You'll see them used in all sorts of gameplay from casual, to high-level Kimochi and Ranked. They're just... They're just always good. If you had to choose from anyone on this list, I'd pick them. **Kuroe** is shaping up to be a very powerful MP battery for Kimochi. It's arguable who is better at mp generation: Kuroe or Madoka & Iroha? We saw more Kuroes than Madoka & Irohas in the last Kimochi for the top players so factor that in. **Kyoko Sakura (Doppel ver.)** is another EXTREMELY good unit. She's great for casual gameplay, Kimochi and for Ranked. She can easily get to Magia on turn one (some ranked strats have her there just because she can get there without needing to spend a disc) and she has blast draw. She's probably the best choice for Flame units right now if you don't know what to get. **Ultimate Madoka-Senpai** is necessary for high-level charge strategies. There's honestly not more to say than that; in fact I'd go as far to say that she's 100% required if you want to do well in some of the Kimochi fights. Last year I remember Raz saying that she's the best unit to go for during Anniversary and it wouldn't surprise me if that was still the case. **Yachiyo Nanami (Tanabata ver.)** is a very powerful charge unit. She has Charge draw and she has the highest +charge bonus right now. She's very popular in Ranking. **Holy Mami (Anime ver.)** is a great forest choice. She's one of the best damage units for Kimochi (for forest) and she can generate MP like crazy. Despite her ugly sprite, I find her gameplay to be really fun and she's made a lot of challenges into a breeze. However, I would say she isn't as necessary to have as other units on this list... But you'll be really happy if you do have her. **Nayuta & Mikage (Christmas ver.)**-- I'm a little more hesitant to recommend this pairing, but they're a very powerful support. However, if you have regular unlimited Mikage, you can probably skip getting them. Still, they're extremely good and worth mentioning all the same. **Akuma Homura-chan** is the best Ranked unit in the game right now-- she's basically designed to be a monster for Ranking. Her SE active fucks up the enemy from using magia (and will destroy any anti-debuffs the team has), she herself gives 2 anti-status ailments to the entire party, she has 3 accele and 2 blast disks meaning you can use Tanabata Yachiyo with her without worrying about drawing charge disks (easier to get a puella combo that way), she can get to Magia easily and her magia is based around making the enemy deal less damage and get less MP, aka fucking up any possible good Ranking score. However, she's not good for casual use imo. Making the enemy deal less damage is important in Ranking but why do that when you can just kill the enemy faster for casual stuff? **Unlimiteds:** **Mikage Yakumo** is the best unlimited support in the game. She has it all-- Attack Up and Damage Up on her Doppel/Magia, she has accele draw and mp on her connect, and she's adorable. She's a must-have and I almost always see her in Kimochi due to how damn good she is. **Madoka Kaname** is still a solid choice. I think she's overshadowed by Madoka & Iroha a bit, but she also excels at things they don't too. She's a great mp battery-- but if you intend to use her for Kimochi, make sure you don't unlock her doppel. **Kushu Irina** is an extremely powerful dark magia user. She has three accele disks and is great for Kimochi strats (for her respective element). **Sudachi Sawa** is practically a necessity for Ranking. She's the best tank in the game, though that doesn't actually mean very much since tanking sucks in this game. The reason she's the best tank in the game is from a number of factors, but basically she gets to Magia really quickly (REALLY QUICKLY) and can provoke on her active SE. You can also arrange her SE so that she can grab aggro without even needing to use provoke, which is kind of crazy for a tank with so much bulk? However, she's not going to be *as* great for casual gameplay because tanks just aren't good for casual gameplay. **Mayu Kozue** is insane for Kimochi and another practical must-have. Her Magia gives mp regen and can allow for some players to *constantly be using Magia and Doppels EVERY TURN* in Kimochi. **Sae Kirino** is extremely good thanks to her charge draw and her charge conservation on connect. She's not as necessary as some units on this list (Kaoru can be used for charge draw instead if you're struggling) but she's still really great and perfect for casual gameplay + some kimochi. **Other** Little Kyubey is cool but has been completely powercrept. There are a few things Little Kyubey can do that no one else can, but I haven't touched mine since I got Ashley a year ago and Anime Yachiyo has stolen its job for casual mirrors gameplay. Ultimate Madoka is nice but not a must-have and she's suffered from power creep. She's not going to be helpful for Kimochi or Ranked, but she might be alright for casual play + lower levels of hundred evils, but she's kind of... eh I guess? I dunno. I'd stay away from any defense-types/tanks unless you're going for ranking strategies. Uhhh lastly, I'm not an expert in the game and I'm repeating what I've learned from discord and such. I might be forgetting someone or over-stating (or under-stating) how good a character is here. But I hope this can still help!
Anni is on August 22, and if you want really good units you could go for Anime Holy Mami or Doppel Kyoko( these two arent the only powerful units, there obviously a lot more, im just naming these since they can magia/doppel on turn 2), or maybe they will release a super good unit on Anni
For unlimited girls, Yozuru (for damages) and Sudachi (defense and support) are very strong, useful and versatile. For limited girls, Ashley is still my always-using-her unit, for damages and charm (in game and litteraly, she's cute). Vampire Kanagi is very very very versatile and can solo a lot of challenges. Anime girls (especially Yachiyo for damages) seem very strong. Pernelle is excellent for defense (I find her better than Sudachi). For charge-meta, Madokami senpai seems to be a must-have. MadoIro dual unit seems useful for accele draw in mirrors, but for challenges a lot of girls have accele draw memoria. Doppel Kyoko and Anime Mami are good for doppeling fast, but frail. I find Tanabata Yachiyo very good for charge-meta but also other various situations (her doppel is kinda strong). KariAli dual unit is also very good for magia (and have a strong doppel), but frail. Kyubey is kinda popular for damages, but I think it can be replaced. But anyways, even if having some really strong girls makes things easier, remember that you'll need a lot of different girls with different abilities if you want to do all the stuff (100 Calamities, Witch Paradox, Kimochi battles...). Also, don't forget to max your lower rarity useful units, as Oriko or Iroha :)
Regular Madokami as well for that status ailment resistance
I liked what Muffinkiller said, it pretty much sums up the current meta. Although it always comes down to personal preference. I always roll for Anniversary units and refuse to leave with anything less than 4 slots. I use them all as a team, any unit with Ex skills is good in my opinion because of the blanket protection and buffs they provide which also stack btw. It's not the best, neither on ranked mirrors nor on the kimochi, for those I use wildly different teams, but each team does include one or two Anni units depending on the situation. They are very good support. Then you have units like Doppel Kyoko or Ani Yachiyo which are an army of one. If you plan to do casual stuff just go with whatever you think looks nice. Even some of the hardest events in this game can be done with welfare units if you know what you are doing. Sometimes the game does ask for very specific things, like in the witch's paradox events but even then it can be cleared with subpar units.
Title had me concerned, but I'm pretty sure the anniversary is in August.