I’ve only run at NCMP once a few years ago for SKUSA summer nats. It’s a fun track for a shifter kart. As for road racing check out http://www.championshipenduro.com/
For buying a shifter kart there’s going to be lots of opinions but personally I’ve had good luck buying used either on ebay or ekn. The next question you’ll ask is what engine to go with and again that’s a tough question to answer. I think most would agree that the newer ICC’s are taking over now but stock honda’s are still pretty competitive.