Hi - have a look here about how to compile budgie desktop.
Basically have a look at compiling the code. Maybe just have a look at some of the compilation warnings - see if you can spot where in the code those warnings are produced and see if one or two of those can be fixed.
Once you are feeling a bit more confident then we can dig in a bit more - working with upstream, having a look at some of the easier stuff on the upstream tracker etc etc.