Everyone who’s ever been to a festival has their must-have items and it varies from person to person. For me, its a bag with lots of pockets for easy access and a water bottle with a carabiner attached to it.
Inside my bag I always have: camera, memory cards, lip balm, eye drops (yes eye drops, they are a LIFE saver especially at dustier festivals) and other small things in a semi waterproof (plastic) zippered pouch so you don’t have to go hunting for them in a bottomless pit when its dark outside. I also always have a pack of tissues, hand sanitizer and gum. I always transfer my debit/credit cards, a small amount of cash, my ID and the festival ticket (if its not a wristband) to a small zippered wallet so if I do happen to lose it I don’t lose the entire contents of my wallet.
Its also important to keep some sort of sunglasses case whether it be hard or soft in your bag because when the sun goes down you don’t want to scratch up the lenses by letting them loose.
If you’re super concerned about keeping your phone charged, invest in a Mophie case or portable juice pack so you can always charge your phone, with or without a power outlet.
As far as water bottles are concerned, I prefer Nalgene water bottles simply because of durability. I have glass water bottles that I love but in my experience they DO break more easily than the plastic ones and theres really nothing worse than broken glass at a festival. Not all plastic is created equal though! If you decide to go the plastic route make sure you’re investing in durable polyethylene, not cheapy plastic that will shatter. Another reason to invest in a Nalgene is all their bottles are BPA free, giving you peace of mind when it comes to health concerns using plastic. Ensure that no one runs off with yours by personalizing it with stickers!
Some more hard core people prefer CamelBaks, which I will make a post about at a later date.