As mentioned, you have two paths to start, NHRA legal, or just "ok" with the track you run at. What happens if you crash, get knocked out, and the car catches on fire? Are you going to trust others to save you, or buy better equipment to try to save yourself?
Some questions to pick the correct gear:
#1 Open wheel car with engine in front (FED & ALT)?
#2 Engine fuel and induction type?
#3 Automatic transmission with no floor?
#4 Petitional MPH and ET?
I would personally stay away from Amazon and eBay, unless the store you are buying from is well known. Believe it or not, buy there is A LOT of cheap knock off junk for sale, and I would hate to see anyone getting hurt because of fake junk. I recommend Jegs, Summit, and Speedway Motors as good vendors. I have not used Good Vibrations, but they fork over a ton of money to sponsor races, and put money back into our pockets. NTF racer Brendan Murry has a similar shop called Performance Motorsports. You will not find a better guy, and he will take parts off his car to get you going.
Gear brands usually do not matter to people, they just buy whatever. I am picky. I buy great products. I highly recommend Simpson Race Products, Impact Racing, Diest/DJ Safety and Bell Helmets. DJ makes great car products. Simpson and Impact make great driver products. Bell makes great helmets, and Speedway Motors bought the rights to Bell Racing, and makes/sells nice Bell labeled driving gear, at a low price.