iv went session 3 and if you pack well it will help you allot more than you think.
Here are some essentials that are easy to overlook:
any kind of jacket is pretty much a waste of space. bring a huge sweater and layer some tees under for warmth (witch you probably wont need anyways).
bring sunscreen and you will make friends quickly. it is usually in high demand after the first day because most people have burned noses.
dont spend your money on clothes and shit that you already have because when you are craving a red bull it kinda sucks to find out that you dont have any cash left. On a related note, Buy your drinks before hand and keep them in the fridge so that you dont have to carry serious bills everywhere because i have lost 30 $ and a cell phone in the foam pit.