If you are shooting in Single Stack division, you will need at least four mags, and six is better. I have one in the gun, four on my belt, and another in my hip pocket that is used for topping-off the gun, but which I restoke in case it may be needed. I do the same for Limited 10. You will want pouches for all of your mags. You can't do consistent reloads from a pocket.
Besides yourself, your gun/gear and ammo, there are a number of things to take to the match, that run the gamut from important to near-inconsequential. Bring money for the match fee. Bring a bottle of water, a hat to protect your head, gloves if it's going to be cold. You might want a notebook, for keeping track of things that you want to practice, or look up in the rule book. If lunch isn't available at the range, take a snack of some kind. I also have a pen, a cleaning rod, bushing wrench, a small collection of spare parts, a calculator, baby wipes, spare ear plugs, spare safety glasses, band-aids, rule book . . . that's all I can think of, off the top of my head.
