Being you already have the gun I would say that IDPA is going to be the most cost friendly competition to get into. All you need is 1 gun, 1 holster, 1 double magazine pouch and 3 magazines. Your cover garment can be a simple button up shirt or the shirt you wear to the match.
NRA Life Member, NRA Range Safety Officer, IDPA Safety Officer, USPSA NROI Range Officer
As you are, I once was, As I am, You will be.