Don't buy "gaming" headsets. They're shit value for the money and usually pretty shoddily built. I'd suggest getting a pair of headphones and a clip on mic. The Audio-Technica AD-700(these just recently went out of production so they might be hard to find) is a great pair of headphones, and this:
http://www.amazon.com/Olympus-ME-52W-Noise-Canceling-Microphone/dp/B000MYPPPE/ is a great mic.
Alternatively for headphones, you can get the CAL(
http://www.amazon.com/Creative-EF0060-Aurvana-Live-Headphones/dp/B000ZJZ7OA/), or if you don't mind spending a bit more, just about anything from Beyerdynamic is really good for playing games. Or if neither of those are up your alley, Sennheiser 558s and 598s are also really nice.
As for keyboard, anything mechanical is pretty nice. I have a Razer Black Widow Ultimate and I'm a fan.