I don't know what's good to help with and what isn't, because I haven't been involved with Rust development for a pretty long time at this point.

Personally I think contributions work best when you're trying to solve a pain that you personally have or at least have some sort of connection to, so I'd encourage you to consider what/how/why you struggled to learn, and then try to fix that. I know it's vague, but it's the best I've got right now!