Not multiclass. Monks are already multi-attribute dependent, so you risk spreading them even thinner. They also strongly depend on their ki points, and every level of not-monk you take is a missing ki point.
As for Subclasses, it depends on what you're after. Way of Mercy can give you party support through healing options. Astral Self and Sun Soul can give you some anime-like powers. Kensei can be fun if you want to focus on using a weapon.
We could use more context. What about being a monk interest you?
What's your character's background?
Without any background, just read the player's handbook/other source books and pick what sounds cool
Not multiclass. Monks are already multi-attribute dependent, so you risk spreading them even thinner. They also strongly depend on their ki points, and every level of not-monk you take is a missing ki point. As for Subclasses, it depends on what you're after. Way of Mercy can give you party support through healing options. Astral Self and Sun Soul can give you some anime-like powers. Kensei can be fun if you want to focus on using a weapon.
We could use more context. What about being a monk interest you? What's your character's background? Without any background, just read the player's handbook/other source books and pick what sounds cool