We know that in order to have a good story, the MC has to learn something. But what is your character supposed to learn over the course of your story?
Well, anything. It depends on a lot of variables such as your character's personality and what you're subjecting them to. Here are a few specific examples of change:
RELIGIOUS. If Aladdin stumbled into a church and was awed and inspired by the sermons and artwork, then he decided to become a Christian, that's a major change. What did Aladdin learn? Christianity. (Especially since he more than likely would have been Muslim, as the Middle East... well, always has been. That region was originally united by Islam, wasn't it?) I would put "religion to atheism" here as well, even though by definition "atheism" isn't a religion at all.
IDEAS. Or idealogies, or whatever. It can relate to religion, but this is broader. For example, Opal (that name reminds me of the Artemis Fowl series, haha) wanted to be a ballerina her whole life, then breaks her legs and is forced to join art therapy by her mother. She finds she loves building sculptures more than she ever loved ballet, and decides to be an artist. This is an ideological change. It includes things like career paths, how they view the world, pretty much their beliefs in general. This is a big category.
CLIQUE. I know, but it's true. If your character is popular and decides that she is really happier off at being a nerd. If your goth girl is suddenly thrown into the world of politics and socialness, and finds that she doesn't actually mind it. If your popular jock announces to the school he's gay and would rather be hanging out with emo kids anyway (I don't see why it's such a big deal being gay or emo, but hey, whatever). I think you get it.
EMOTION. If your character is always happy, then goes through a torture session and ends up perpetually angry. Your character is grieving but finds a way through it. In a way, this can connect with all three of the above.
Basically, your character can only go two different directions - they can turn good, or they can turn bad. Usually good, but one of a good guy turned bad would be awesome to read. Those categories above are specific ways that change can happen. It can happen in a sudden epiphany, or so gradual, your character doesn't notice until they look back. There are infinite possibilities from those two choices.
There are more categories, and this barely scratches the scratch on the surface (I cannot remember where I get that particular saying - some book. Just know that wasn't mine). But this is a place to start.
Have a blessed week, keep writing, and love books! <3