First, congrats on taking the plunge. I hope you enjoy it!
Shoot a platform that you are familiar with and shoot a specimen of said platform that is reliable. If you shoot Glocks and have a good one, start with that. If you shoot 1911s and have a good one, shoot that. Shooting something you are familiar with and know works will increase your confidence and decrease your headaches.
Set a simple goal(s) for each match. Your first match goals should be to maintain safety at all times, finish the match and not disqualify, increase your knowledge of the rules, and get the phone number of at least one experienced shooter whom has consented to let you bug the crap out of him/her in the period of time between the first and second matches!