Just like Tom has advised you its best to see what others are doing with GP and try to reproduce their work (even if its just to learn all the possibilities without copying their work in your final product),that’s how i started out myself. You can also ask how others customize their sites
One other thing that will be of immense help is to go through this excellent support forum and try to see what support questions people have been asking and try them out,you will be surprised how much helpful that can be.