First of all, ya gotta remember why they call it a "uniform" - so's ya look more-or-less like everybody else. Senior NCO's will spot the smallest piece of non-regulation clothing or equipment from 20 yards away, and will jump all over your case in a heartbeat. The idea is to wear what everyone else in the unit is wearing, and not to be obviously different.
GI-issue BDU's are where you start, buy a couple of sets from your local Army-Navy surplus store or online from Ron(greenmountaingear). Texas being much like Arizona, I personally recommend you go with 100% rip-stop cotton BDUs for comfort in the summertime - however, they're not quite as sturdy as the NYCO(nylon-cotton blend) BDUs, and tend to wrinkle and fade more. NYCOs are hotter, but look nicer and hold up better over the long run. Be sure not to buy Desert BDUs when the rest of the unit is wearing Woodland Camo - check first before buying. Also, get a couple of brown or OD green undershirts to wear with your uniform - white T-shirts are a big no-no with BDUs, they look all wrong.
You'll probably need to have a unit patch and embroidered nametags sewn on to your BDU shirt(blouse) - don't try to do it yourself, unless you know exactly how they're supposed to be positioned your sewing will look like crap. Find a tailor shop that's close to a major military base - they will either know how to do the job properly, or they will tell you where to go.
For headgear, start with the basic BDU cap - it may not be right for all occasions, but it's never "wrong." "Boonie" or "jungle" hats are only worn on field exercises, seldom if ever in "garrison"(around barracks, unit offices or other, improved facilities). Don't be a "wannabe" and buy a beret UNLESS and UNTIL you're told to by someone in your chain of command. Like Ron said, hold off on the Kevlar helmet until you're told specifically that you need one, and then look for the cheapest one you can find online or at a gun show. If you shop carefully, you can probably find a PASGT(Kevlar) helmet for $50-75. Try to get a new replacement sweatband for it, instead of the nasty, funky one that will probably come with it.
For your load-bearing equipment(LBE), start with the GI pistol belt and Y-harness suspenders. The H-harness suspenders are a bit more comfortable, but date back to the Vietnam era and will probably be kinda raggedy by now - a newer Y-harness will look more "strack" and be more presentable. Add two 1-quart plastic canteens with canteen covers - can't carry too much water, especially in Texas during summer. Get two compass pouches - one holds your compass, the other will hold a field dressing(first-aid compress/bandage). Add two GI M16 magazine pouches, and that should be about it. Don't go overboard hanging too much stuff on your LBE - you'll look silly and be uncomfortable. Hold off on the snazzy Bianchi UM84/M12 GI nylon flap holster until you find out if you're actually going to carry a pistol on duty. The same goes for entrenching tools(GI folding shovels) and "buttpacks"(3-day combat packs). DO NOT strap a Ka-Bar or other combat knife/bayonet onto your LBE UNLESS and UNTIL someone in your chain of command tells you that you may do so. Try to get someone from your unit to help you adjust your LBE for fit - it goes about 3 times faster with help than if you do it by yourself. Get some OD green duct tape("90 MPH tape") and use it to tape down all the loose straps.
Boots will be black, UNLESS you are authorized to wear Desert BDUs along with the rest of your unit. For now, just get the basic, all-leather GI "Speed-lace" boots, and a shoe brush and can of Kiwi black shoe polish to keep 'em looking neat. Don't spend extra money on fabric-sided "jungle boots" or Hi-Tec-style "SWAT boots" unless your unit chain of command specifically allows you to wear them. A pair of all-black Doc Martens or Red Wings work boots should also be fine, but in order to look "right" with BDU trousers tucked into their tops the boots should be 8" - 10" tall.
Hope this helps!
