The big thing I have learned with any skill is just doing it. If you want to play in a band and write music than just do it, no need to spend years practicing before you start, your ready right now.

Some really great bands have been formed by people who could barely play their instruments and their music reflected that but it was still great music because they wrote it well. You sound like you can play so just form a band with the most like mined people you know and start playing. Get your stuff out there and get peoples reactions. Do what you want and don't listen to them but let them listen to you. Just make sure that whatever your doing your doing what you want.

Play, play, play. write, do whatever. Just do it. whatever that is. don't wait.