My DS brought a bunch of stuff he didn't need, e.g. powerbars, travel alarm (obviated by a watch or phone with an alarm - and apparently when it's time to get up, the detailers made it eminently clear
). I don't think he even needed an athletic T or shorts - I just list them as I figure it's good to bring one of each if there's a problem getting your issued gear. They receive multiple shirts, shorts and a sweatsuit which they wear everyday. All he needed was:
Underwear (7)
Athletic socks (7)
Athletic shorts (1)
Athletic T-shirts (1)
Running shoes (2)
Swim trunks (1)
Polo Shirt (traveled in)
Khaki shorts (traveled in)
Shower flip flops
Towels (2)
Toiletries (bring a razor)
Twin size bed linens and pillow (you need these)
Sports watch
Photo ID (required)
Cell phone and charger
Black garbage bag (bringing home wet, muddy clothes)
Sun block
$100 (for airports, emergency, taxi, etc. - didn't spend money at USNA).
Honestly, I can't remember whether he even needed that many changes of boxers or socks, or the extra running shoes. I think it's just precautionary for days you get completely wet and muddy and may prefer a dry pair of shoes the next day.
By the way, my DS had a blast. He was uber-impressed by his peers, the cadre and the officers/NCOs, and loved meeting kids from all over the country and world. We have family history there and had visited before, but NASS sealed the deal for him and he is PUMPED for Plebe Summer next month. Best of luck!!!