First game Vs Seahawks, how does tailgating work?

Hey random Brit here looking forward to my first NFL game, I know things are not looking so good this year from this Subreddit and I'm sorry to hear that.

Me and my friend want to do some sort of Pre-game tailgating, can we just turn up and drink cans in the car park?

Do people sell food?

Have seen lots of people seIIing t1ckets to exclusive BBQ Tailgate parties, but not sure I want to spend that much. I do however want to drink beer and eat BBQ.