Id,money,change of clothes and any personal hygiene products you would like. They give you stuff if you don't have it but I would take my own. Smokes are ok to bring and after 5pm you can change into your civilian clothes. They have a soda and candy machine that you can also use.
Be nice to the Soldiers there with you on detail,they might be nice enough to pick up some things for you at the PX.
I had a short stay in the PCF due to a missunderstanding and I was able to leave the base after 5pm and sometimes I brought some of the guy's back stuff.
Good Luck,you're making the rite decision.