I went to OCS in 2011 so anything is up for change since then.
I took a lot of stuff. A lot more than I needed to as we had a lot better access to the NEX than we thought. Things I remember wishing I had brought was the stuff I actually had my wife send me, and it's all personal preference stuff that you can't buy at the NEX. I don't like Kiwi shoe shine, I like Lincoln brand stuff (someone at OCS had a tin and let me try, it is a lot better) and the aforementioned Fox River socks.
Anything else you can pretty much buy while you're there and you might be able to share with others. Cleaning supplies you pretty much have to buy there. But if you have these things, then I would bring them: cuticle scissors, clear nail polish, super glue. It really doesn't take as much as people build it up. You will also need slightly more than 7 pairs of underwear and socks, at least at first laundry does not run smoothly.
Things I bought there that I am glad I did: Extra boot socks, extra shirts, extra towel, extra shower bag, extra set of sweats (for sleeping in winter, new building might be better)
Things I bought that I regret (or that others bought):
- So many white crew socks. So many.
- Books. It is tempting because a lot of OCS is crushingly boring, but there are free books floating around there. Now I have like 3 "how to be an officer" books that I read most of on watch and will probably never read again.
- Iron/ironing board. If it hasn't changed there are piles of these floating around. They are all busted up, but what is your new $50 iron the first time you let someone else use it, or someone bumps you in the hall? Equally busted.
- Vitamins. Maybe just our class, but when class team let us we all went crazy for buying vitamins.
- Any expensive item, just for RLP. Buying an extra pair of pricey boots or shoes you won't wear again, just for RLP is dumb. You are not going to fail because you have worn an item, you will fail if it is apparent you didn't put in the time and attention (or the mood strikes to fail you, depends on the day)
- So many PT uniforms. I don't know how many were issued. But I have worn the official PT uniform only a few times since OCS (YMMV, that depends on command, community, how you PT, etc...) but I have a whole drawer of them that I came back from OCS with.
This is all my experience, from 2011, so take it with a grain of salt.