There are tons and I mean tons of holsters available for your Glock. I carry mine in a Comp-Tac MTAC IWB holster. It's pretty new to the holster market, but it is well worth the price. Do you prefer OWB (Outside Waist Band) or IWB (Inside Waist Band)? OWB is much more comfortable, but you lose the ability to conceal really well, and IWB is the exact opposite. I like the Blackhawk CQC Serpa holsters for OWB carry, and they can conceal fairly well. If I were you, I'd find a store that has a nice holster selection, and try a few to see which ones you like the best. Many people find themselves having a box of empty holsters in their closet. Fortunately I have not had that problem.
As for mag carriers, well to me they're all the same. You have single and double mag pouches, and choice of leather, kydex, or nylon. I don't carry a spare mag in a pouch, I just put it in my left side pocket.