The footwear you choose can sometimes be dependent on the festival you're attending so if you're heading to Glasto it's wellies you should don, especially as the days go on because it can get hideously muddy! Whereas if you're going to Wireless a pair of ankle boots will do the job nicely, for the first day or two at least. I've seen so many photos of people wearing trainers or sandals in muddy fields because they didn't plan appropriately and they just look so soggy and uncomfortable! If you're going to a small music festival at the beach or in Hyde Park and the weather is going to be good then wear sandals but otherwise I wouldn't recommend it.
This weekend I'm heading up to British Summer Time Hyde Park for my best friends hen weekend and as the weather is supposed to be dry I've packed both sandals and ankle boots, mainly because we'll be dressing up a bit 'rock-chick' so ankle boots are more appropriate but if it's too hot I'll likely wear my rose gold sandals.
I've picked out some of my go-to festival shoes from my go-to shoe shop, Spartoo, that I'm sure you'll like. :)