Pack your stuff then fling half of it away. Be ruthless just take what you need. You don’t need much.
This isn’t exhaustive but you’ll not need much more than a 15 quid Tent, roll mat, sleeping bag, enough clothes to keep warm at night and a few changes. Waterproofs(head to toe). Baby wipes, bog roll, Beer, spirits, mixers, weed, mdna, fags, skins, lighters, Money, cards, Phone, phone charger. Chair. Painkillers, immodium, sun cream. Not really much else you need.
Figure out how much trekking you need to do, some festivals you can walk for miles. So take a trolley of sorts, this will enable you to carry more beer. If you want to be really smart make sure said trolley can turn into a sledge if it gets muddy! 😆
Keep your valuables on your person at all times. Don’t take anything you don’t want to lose.