Is there a good guide out there on reverse engineering mobile apps for iOS & Android?
CharlesProxy is a must-have whether you're a dev or reverse-engineering.
JADX is the best for reversing Android because it produces readable Android code which is fantastic for current Android developers who expect things to be organized like Android Studio.
If they pin certs it can be harder but not impossible.
If you want to get started, start by poking at something simple (e.g. your own app). Then google as you run into specific issues.