Congratulations on getting your ticket, it's an incredible festival.
Sure a few people will have answers for you but here's mine...
Food ranges from £7-10 on average for a meal. A burger or similar around £5.
Beer is about £5, there are some variations bar to bar, but as a general guide.
All types of alcohol including spirits are available, but if you have a favourite it's definitely cheaper to bring your own. Just make sure you decant it into a plastic bottle or it will be confiscated by security. No glass on the farm!
Glasto is definitely LGBT friendly, the NYC Downlow venue in the Block 9 area is modelled on a New York gay nightclub. No moustache no entry! You shouldn't have any trouble (although it's basically a huge city for the weekend so there will always be some arse holes). I have never seen or heard any homophobia.
Walking times depend on the weather and ground conditions. If it's dry I'd manage that walk in about 40 minutes during the festival with lots of people about. In the wet/mud it could easily take me an hour. It's a big place.
I've never camped there cos I like it to be quiet ish when I get home but Pennards Hill is meant to be the place for partying. Busy, as near as you can get to the action camp wise. But you'll need to be through the gates quickly, that field fills fast on Wednesday!
Check out this site, all you could possibly need to know is there!
Have a great festival.