Go to the OCS website and look at what's in the bag issue. That's what the cash is for. You might be able to drop some stuff like pencils if they get issued there. Bring a ton of medical tape, but make sure it is THE CLOTH KIND. Don't be the one trying to mark your gear with vinyl tape.
Take bar soap instead of body wash. Body wash doesn't work well enough without one of those stupid sponge thingies; especially in getting the muck off your ass after events like the IMC. Yeah, you can use bar soap on your head. When it gets later in the cycle and you know what htey expect of you, try something different if you want, but barsoap is the way to go in the beginning.
Body glide is gay. Just take a can of vaseline. Despite the negative stigma of vaseline in an all male environment, trust me on this. When your fire teams hams are all chapped up and you want to help them out somehow are you gonna want them to be rubbing your bodyglide all over their asses? Vaseline they just dip their fingers in it and it works like a damn charm.
Good to go on the wrinkle free trousers. Basically no cotton. Don't get gypsy'd into a mostly cotton trouser because the label says wrinkle free. This is an absolute must if you want to leave early enough to still be able to do anything on the first night of libo.
550 cord is also called parachute cord and it's just a nice thing to have in the field. I might buy a pack, but I'd only take about half the pack. Don't be a weirdo and bring a whole spool or something stupid like that.
A giant sharpie is a great idea, but don't be that jackass who stencils his name with it and has it bleed through to the front...."You wanna be nasty? Good...That's an essay." And along with a couple of regular sharpies, bring wet erase markers. Why? Because when you mark your medical tape with a regular sharpie it bleeds like hell. The wet erase markers barely bleed at all so it looks WAY better and the one that comes in your bag issue lasts about 5 days.