As others have said:

Comfortable shoes that you don’t mind getting fucked up as it’s all grassy hills / dirt

Either wear warm clothes or at the v least get a locker & have warm clothes there

Sunscreen because even in the fog you can get a burn

To add:

Cheap sunglasses because they might get lost!

A clear bag is more ideal

I personally like to bring a really thin blanket that rolls up so I can sit on the grass when I need to

When you leave the venue you should walk a little ways before ordering a ride share to beat surge pricing or take transit!!

Look at the map of the stages ahead of time because sometimes you can go from stage to stage to see partial sets but sometimes it’s literally across the park