I live in the UK and I've attended GC for the past 3 years. It's expensive but it's worth it (in my opinion).
The flight will be expensive so try and find someone to room share with, cut some of your costs that way.
Knowing a few people before you go can make things easier and belay the fear that you won't know anybody. However, even if you don't know anyone before you get to GC, it's a really easy place to make friends.
Convince your Geekly friends to stay on a few days longer at an AirBnB, or spend a few days in their state after, you're coming all this way, might as well make the most of it.
Keep an eye on flights and work out the best time to buy. I saved £400 on my flight this year by delaying purchasing for a couple of days.
Don't forget to get an ESTA.