Just finished season 2; understanding the full story without spoiling past

I just finished season 2, I’ve heard a lot of people say they butchered it but as someone who has never read it & fucking loves the anime, I thought it was great. There was so much I didn’t understand though, a lot of the whole story and concepts, characters especially in the last episode, etc. I want to read up on it but I don’t want to read the wiki and spoil stuff for myself. What do you guys recommend other than reading it? I just started a new job and I simply do not have time to read anything except documentation right now. I’d love for someone to explain it to me but I’m sure it’s so long no one wants to do that 😂