• wellies
• many knee high socks
• waterproof rain jacket (you'd be suprised how many rain jackets aren't waterproof!
• funky sunglasses
• festival hat
• shorts
• a small tent
• lots of spare tshirts
• lip balm
• no stupid clothes that you know you won't wear
• phone with a good battery life and credit
• bangles to look cool
• baby wipes
• dry shampoo and deodrant
• suncream
• toilet roll (nasty)
• sleeping bag
• black plastic bags to keep everything dry (tent doesn't work for this)
• 3/4 separate black backs each with complete outfit in each
• dry food
• timetable of acts and what stage they're on
• bottles of water
• chair
• about €40
• small mirror

and try to bring all of this in smallest bag possible!