There have been so many disparities on this topic based upon info from the Academy, this site, parent handbooks, and current mids with whom my DS has spoken:
Some say bring nothing but your running shoes on your feet and the clothes on your back.
Some say bring that plus a few days of toiletries.
And other say those plus a few days of Ts, briefs and socks, and some say even compression shorts.
Can it be safely said that all the above are correct, depending on your detailers/platoon/company?
My DS has resigned himself to his running shoes on his feet, clothes on his back and a zip lock bag with mini-travel toiletries. We've heard recent stories of some detailers confiscating compression shorts brought with you and that underwear/socks are unnecessary. The only reason he's bringing the toiletries is, well, if he needs them for a couple days, he'll be glad he has them. Otherwise, that $10 worth of toiletries can be immediately trashed. We're confident he'll receive underwear and socks, and we'll mail his compression shorts and some of his boxer briefs the day we leave.