Ordinary clothes for everything else (and don’t forget that there are some recreation periods!)
Extra blankets (it may be hot outside, but sometimes pretty chilly inside)
Towel, washcloth, and soap (showers are available)
Swim suit/trunks for showering (showers are outside)
Something to sleep on, in, or under, like a sleeping bag or sheets and a blanket, as well as a pillow. (No beds are provided, so you are sleeping on the floor unless you provide otherwise).
Personal toiletries
Musical instruments (like guitars, flutes, etc.) if you play