When it comes to racing helmets there is no substitute for test fitting. I have had about 10 different helmets over the years for numerous types of motorsport. Dirtbikes, street bikes, race cars, go-carts, open face, closed face...I have quite the collection!
Some of my helmets have been a bit snug and too tight or too loose or have a weird crown in the back that hurts my head, others have fit perfectly and I'm extremely happy with them.
Right now I have an HJC AR-10 which I absolutely love!!! It is the most comfortable helmet I have ever owned. My Dad tried it on one day and he hates it. It was too big, he did not like how large the eye openings were, he wanted the visor to raise higher. But, for me I could not have designed a better helmet myself. The best part...It only cost me $150.00 if I remember correctly.
HJC AR-10 in white:
http://www.hjc-motorsports.com/ar10.htm
So far I have owned:
HJC
Bell
Simpson
Impact
arai
and a few others...
It really just comes down to trying them on and testing the fit for yourself.
The most important thing is the Snell crash testing. As long as the helmet has passed the latest SNELL testing requirements that's all that matters. The rest comes down to personal comfort. Other than the crash testing certification, the comfort is the next important factor. When you do wear it, you'll be wearing it for long periods of time and you don't want to lose concentration because you have an uncomfortable helmet that is giving you a headache. Just because a helmet is pricey, doesn't mean it will fit your head perfectly.
I recommend going to some local motorcycle shops and test fitting different manufacturer's and sizes and just seeing what you like. If you have a local race shop or distributor nearby you should also stop by there and check them out as well.
In terms of race suits. It all depends on what you want to spend and how flash you want to go. My race suit is from a company called Flamecrusher. They are based out of New Zealand and I really like the suit. Very comfortable, relatively inexpensive and it suits me well. I also have a suit from MOMO which is a lot nicer, it's more expensive, but it looks 10 times nicer. Comfort wise, I'd have to say the MOMO is a little nicer. The Flamecrusher has a tendency to get too hot and a little itchy after an hour or two.
Alpinestars also makes a really nice suit if you want something at the higher end of the price range.