Don't buy anything right now. Find out what matches are available in your area, and show up with what you have. The only thing you need is a holster that covers the trigger, and some mags, and of course the ear and eye protection.
Everything else you will find out when you shoot. What works for USPSA, doesn't always work for IDPA. No sense spending money until you know.
I don't know of a match director that wouldn't let you shoot what you have the first time, unless it was a safety factor.