Stay away from the ultra budget stuff. I would not use anything less than a 2 layer suit and SFI 3.2A/5.
There is a large company that is selling single layer private label SFI 3.2A/1 gear, it scares the hell out of me to imagine wearing that in a fire.
3.2A/1 is rated to protect against 2nd degree burns for 3 seconds.
3.2A/5 is rated to protect against 2nd degree burns for 10 seconds.
I'd happily pay the extra $100 for 7 seconds
Personally, I use RaceQuip and NecksGen, but that's because I sell it, so I'm biased.
Saferacer.com has a great selection and variety, and often has closeouts of last years designs for a good discount. Actually bought myself a set of Alpine Stars gloves from them this spring because they were on clearance for half price, and I always wanted white gloves.
Make sure you don't accidently buy kart stuff, and make sure you buy SFI tagged gear.
Jim