-Small uniform items like extra flight caps, soft and hard ranks, rank stiffeners, watches, etc are the kinds of things that you don't need until you desperately need them. Don't bring your own personal AAFES, but I know cadets in my flight who were forever thankful to wingmen who could spare them extras. Also: extra stamps make friends, as well as good spare pens.
-Extra sneakers seem like a stupid thing to worry about and carry until it pours at JFTC and you're the happy cadet putting on dry shoes surrounded by your miserable flightmates whose feet are wet and cold and sad.
-Nice, high quality socks are expensive and worth it. You'll be on your feet so long that it's incredibly important to take care of them. Bring a few pairs that you don't mind getting all jacked up by the little black rubber pellets on the turf at combatives (I'm still picking those out of my nice socks...sigh) but nice, thick socks will roll better for your drawers and make your feet happy. Half calves are way more fly than ankle socks, yes, but you'll be required to keep them "motivated" (all the way up, not drooping) and that's just one more thing to get yelled at about.
-Putting the stuff you're required to have on your person at all times (orders, ID, 341s) in an ID-sized jewelry baggie will make your life way easier during supermans and when you're asked to show that you have those things. These bags are available online and in the jewelry section at craft stores (and possibly at big box stores). Refrain from calling them dime bags. Bring extras to max for those poor souls who show up with their stuff in a gallon bag and immediately struggle to keep it neat and from falling out of the pocket of their PT shorts.
-Make sure your black notebook is pretty sturdy. By the end of Max mine had been sweated on so much that the cardboard cover (your FTM specifies plastic anyway) was falling apart and the lines on the page were all bleeding together- great for authenticity in letters sent to friends, not so much for actual note-taking (which you'll do a substantial amount of). I found that 100 pages was not enough between letters, class notes, and journals.
-Regardless of your skin type but especially if you burn easily, invest in sunscreen that you can apply on top of sweat (you'll pretty much always be sweating) and will stay put. I burn instantly but I did fine at FT by applying sunscreen every morning during personal time, then reapplying a few times throughout the day. It's likely that you'll donate some to be carried by your flight's safety officer, so having two smaller bottles as opposed to one big one would be useful. I bought Sawyer Stay-Put Sun Block and really liked it, but having a spray is useful too.
-It's at the discretion of your FTO/FTU cadre as to whether or not you're allowed to keep non-prescription meds and supplements, but I brought and was allowed to keep orange-flavored Vitamin C tablets that were good for both morale and not getting as sick as well as tylenol. Sure enough, something's going to hurt after those 16 hour days.
-So, you're supposed to have time to shower every day, but sometimes for us that became less of a shower and more of a rinse. I brought face cleaning pads that everyone in my room enjoyed because it made us feel a bit less grody. I'm not going to say there will be days you'll take wet wipe showers instead of real showers because you've got other priorities, but....bring wet wipes too.
-Make sure the things you get are all the same or at least similar sizes. For example, my det ran out of small PT shorts and asked if I just wanted to take mediums, resulting in me having a mix of the two that just never looked neat regardless of how well they were rolled.
-Bring a six-inch ruler for bed-making purposes.
For ladies:
-Sports bras are a must. Make sure they won't fall apart or bleed in the wash and that they're supportive enough to stay on all day. I brought a hot pink one with me after my POC told me not to, thinking that I knew better and it wouldn't bleed, and whatever is in the water in Alabama had my skin and PT shirt solidly pink after PT one morning. Lesson learned! There's really no need for you to bring any regular bras and your drawers look neater with just the one type.
-Spandex compression shorts are also a must. Buying eight pairs is going to be costly but so incredibly worth it. Again, make sure they're good quality and won't die in the wash or ride up on you all day. The laundry schedule can get questionable for both training and practical reasons, and having to deal with normal cotton bikinis while drenched in sweat and on a short time hack in a porta potty in Mississippi in July is not an experience I ever want to repeat. Also- don't be that girl who brings thongs. Like really? Ain't nobody got time to worry about panty lines or looking cute at FT and chafing is to be avoided at all costs.
-Make sure you can get your hair into a PT-proof bun with no bits sticking out within 10 seconds. For me, this meant cutting the layers out of my hair and celebrating graduation by heading straight to the salon to get it fixed. FT is also not a good time to experiment with cutting all of your hair off. Bring gel or hairspray that comes in a sturdy bottle and will stand up to the humidity.
-Because you'll have some quick showers, consider bringing a 2-in-1 shampoo and a leave in conditioner that you can apply later when you've got a moment. My room shared a bottle of argan oil that definitely kept my hair from becoming a nasty, dried out mess. The nice smell made us happy.
-Hiding makeup in your security drawer to apply at graduation is tacky. Show off those graduation and airport pictures where you look underfed, sunburned, and approximately 14 years old with pride!
-Tampons x1000. The physical and emotional stress of FT will mess with your cycle, guaranteed. Even if you're on birth control or you think you've got a super regular cycle. Even if you get it the first week and think you'll be fine for the rest of the time, or aren't supposed to start until the last week. At the very least, having a ton of tampons and always keeping some in your ABU calf pocket will save you or your wingman.