What to wear to outdoor festivals?? (t in the park, leeds, reading etcetc)?

Hihi, iam a female and this year iam going to some of the big music festivals, at these iam going and camping over the weekend at them, what iam wondering is what i should take, in terms of clothes, to let you know i get really cold lol. also when i get there i will be buying band t shirts from the small shop things there, and i will want to wear the t shirt, so e one can see and i dont know what to do then, because i will have my other clothes on at that point. all i really want is help on what to wear coz i get cold and how i can wear the t shirt when i buy one??? thanks
Answer
Thermals under whatever you take waterproof mac wellies dont take gucci or designer jeans, old is nice you will get covered in muck, i always take stuff i can lob away afterwards. thermals waterproofs and wellies are the main thing