For production you will probably need a minimum of 4 mags and preferably 6. Most courses of fire will be 18-32 rounds. You are limited to 10 rounds in production. It is always nice to have an extra mag or two for missed steel or feeding/mag jams. Eye and ear protection. Mag pouches and a production legal holster. Plenty of ammo and a gun bag/case to carry your pistol in to the match. Some extras to consider; hat,water,cooler,snacks,bug spray,sun protection, and a small towel. Most of these are assuming an outdoor range.
Welcome, DVC.
Randy