What bag should i take to reading festival?

It really depends on how far you're walking and how much you're carrying. I go to festivals every year and in my humble opinion nothing beats a good sturdy rucksack. I took a bag on wheels once and it was the worst experience ever because it rained and the ground turned into thick mud. I was definitely wishing I'd brought my rucksack that day. So check the weather predictions before you go. lol :-)