You can pick up inexpensive holsters and mag carriers at OPS (oklahoma police supply), like Blackhawk or Uncle Mike's brands here in Tulsa. Uncle Mike's holsters aren't technically legal for IDPA, but most match directors or safety officers will let you use one to get started with until you find something more suitable. In fact Jack Ostendorf, the match director at Oil Capital, loaned my son one to use during our first match. Holsters and mag carriers made out of Kydex for IDPA/competition, are cheaper than say a high dollar carry rig like a Milt Sparks VersaMax 2. Also, kydex is very fast on the draw and offers easy one-handed reholstering. Just keep the inside of a kydex holster clean so that grit doesn't accumulate and scratch your weapon, of course this would be true for any holster, regardless of the material its made out of. Ky-Tac and Comp-tac are popular brands. Holsters can be either clip-on or have loops for the belt. For Revolvers, Ready Tactical Products is a popular brand besides those already listed.
Ideally, if you carry concealed daily, the best training is to use your carry rig (holster and mag carrier(s)). So if you have that, use it, otherwise, pick up something inexpensive...and in stock as the high dollar holsters can have long wait times (like the 20 week wait for a VM2 right now).
IDPA - .45 caliber single-stack semi-auto weapons like 1911's:
You'll need at least 2 magazines and 3 are recommended. This is assuming it's a full-size gun and takes a full-size magazine. 7 or 8 round mags are recommended. Base pads are also recommended.
IPSC/USPSA - .45 caliber single-stack semi-auto weapons like 1911's:
You will need at least 4 magazines and 5 is recommended. You can use 10 round mags and shoot Limited-10.
IDPA - 9mm and .40 caliber double-stack semi-auto weapons:
3 magazines are recommended.
IPSC/USPSA - 9mm and .40 caliber double-stack semi-auto weapons:
I believe 4 magazines is the minimum with 5 recommended.
Revolver Shooters - You will need at least four for IDPA, one to load and make ready and three for the stages. Popular brands for revolver speed loaders are the Safariland Comp II (better) or Comp III (best) speed loaders. Jet Loaders available from Brownell's are also a top choice. I don't know many of the specifics about revolver gear. I would post on the forums here, there are a few guys that shoot revolvers and are as fast as the semi-auto guys. Jerry Biggs (Glocktogo) is awesome with a revolver (or anything else he shoots).
In IDPA, 10 rounds is the maximum that you can load in a magazine, even if the magazine can hold more. For most stages, you can load one in the chamber for a total round count of 11 to start the stage with. Some stages will require a specific number of rounds, like 6 rounds total to start, then reload with a full (10 rounds) magazine during the stage. Each stage will specify the number of rounds required and the number of rounds to start with if it is less than a full load (10 in the mag + 1 in the chamber). I don't know the rules for magazine capacity for IPSC/USPSA, but I believe they allow you to load your magazines to full capacity with the exception being the Limited-10 class that has a maximum of 10 rounds. Someone correct me if I'm wrong here.
Spare Mag Carriers:
IDPA - You'll want a minimum of two spare mag carriers, this will allow you to have 3 magazines for each stage. For revolver shooters, you can get away with only two speedloader holders if using a vest and put the third in an easy access pocket, though some run a third holder behind the gun.
IPSC/USPSA - I don't know the specifics here, but I would assume you would need enough to carry your spare mags (mags not already inserted in the gun). From the IPSC pics I've seen, those guys have mag carriers everywhere!
You will need a decent gun belt, something that will support the weight of the weapon, holster, mag carriers and full spare magazines. A 1.5" gun belt is the norm.
You will need some form of eye protection to protect your eyes from ejected brass. This can be shooting glasses (yellow lenses) which are great on cloudy days, safety glasses or most types of sunglasses that completely cover the eye. Make sure they properly cover the sides of your eyes, like the wrap-around styles.
This can be ear muff type or ear plugs. Some people wear both. The noise-cancelling ear muffs are nice, but not required, because you can still hear normal conversations while wearing them but they still cut out the sounds from gun shots.
For IDPA, any cover garment will work. So just wear whatever you normally wear when carrying concealed, like an unbuttoned shirt (long or short sleeve depending on weather), jacket or coat. You can also use a vest if thats your thing. They make 'tactical vests' that have a lot of pockets, so those who wear them will often use those extra pockets to drop spent mags in during a stage.
IDPA - Typical match requires 90-120 rounds. I always bring 150 rounds to be safe.
IPSC/USPSA - Typical match requires 120-150 rounds.
Most 9mm shooters buy the cheap Blazer ammo at Academy Sports. As of this writing, the price is around $5.67 for 50 rounds. For other calibers, check prices at Wal-mart also. Reloading can save you some costs. Your cost saving results will vary depending on the caliber you shoot. You won't save much for 9mm, but you will for .357 Sig, 10mm, .40 and especially .45 caliber.
I always bring a couple of bottles of water. There isn't much time between stages and most ranges don't have water close to the bays where you shoot. This will be more importand during the hot Oklahoma summer months. You need to stay hydrated.
Its kind of nice to have a little caffine boost towards the end of the match if you feel a little tired. When its really hot out, I'd recommend water over caffinated drinks though, to keep you properly hydrated.
Some type of granola bar, energy bar, trail mix, etc. Remember you might be on the range for 5-7 hours, so you may get hungry and need a little energy.
Keeps the sun out of your eyes and will keep your head from getting sun burned.
No explanation needed.
Sneakers or tennis shoes. You will likely be standing during the entire event and will walk a pretty good distance. Keep in mind that if its been raining or might rain before or during an event, the range can get muddy, so don't wear your sunday-go-to-meetin' shoes. Some of the ranges are better than others as far as being muddy during wet weather.
You will have scoresheets for each stage that you will have to fill out with your name, stage number, class, etc. The range may not have enough spare pens for everyone.
Small assortment of tools, to adjust your holster tension, mag carrier tension or disassemble your gun if needed to fix a problem during a match. I carry a phillips screwdriver for my holster and mag carrier tension screws and my Glock armorers tool. You may never need them, but if you do, you'll be glad you had them.
Not a requirement, but nice to have if you break a spring or other common maintenance part during a competition. This will vary according to your specific weapon.
You need a bag to carry all this crap around in. I actually use one of my son's old school backpacks because all this gear can get heavy (gear + ammo) so throwing it over your shoulder makes it much easier than just carrying it with a handle. Many prefer range bags because they have lots of different divider pockets to divide all your gear up and some have shoulder straps also. The good thing is that as the day goes by, the bag will get lighter as you shoot up the ammo you're carrying and drink your water or other beverages.
Conclusion:If you carry concealed, chances are you already have 90% of the required gear. Matches cost $12-15 and if you shoot 9mm, ammo is cheap too. So it really is cheap fun. It is a blast to shoot and the matches are always challenging. Plus its a great group of guys/gals, always willing to help new guys out.
You should give it a try, you'll love it, make new friends, get a little sun and fresh air, get a little exercise, and it will make you a better shooter.