Wow, $2000! If you've already got the guns I'd say $3-500 on holsters and mags (I recommend at least 5 for each gun, if only because that makes the IDPA Classifier easier to shoot). I assume you already have eye and ear protection and a suitable concealment garment. Get your own electronic timer if you have somewhere to practice that allows draws from a holster and relatively fast shooting.
Spend the rest on some good training classes and lots of practice ammo.
Welcome to IDPA. You'll love it!