The best way to get in and learn c2 or c3 is to just get in a learn :) in my opinion anyway. Start small, then try and build something big, get stuck, pull your hair out trying to find the problems etc
Most questions you will have someone else has probably asked so making good use of the forums will help.
Here is also a big list of tutorials you can still access.
Whichever approach you take I hope you have fun.