The couple of 3 guns I shot, it was a good idea to bring enough mags to equal 40 rounds of pistol. Pump shotguns are fine, gonna be a little outclassed with the semi's but most of us were out there to have fun. Optics aren't necessary, and since this would be your first match, I'd personally pull them off so you stay in limited and don't get put in open. On the pistol ammo, personally if you are running 9mm, I'd run +p ammo on any stage with pepper poppers. Per the rules they are supposed to be set where a regular 9 mm load will knock them down if they hit in the upper 1/3 only. This is meant to equalize the 9's and the .45's. Shotgun ammo I think the most popular 12ga load was #6 shot. Granted I haven't shot these matches in almost 2 yrs so they may have changed a bit. Also Hip holdsters only for safety reasons. No Inside the waistband, cross draw, thigh holdsters.
Contact for SRGC IPSC is Cindy Noyes 770-460-7436 Give her a call, and if possible it's a good idea to meet up the day before for target setup, and runthrough pointers