The cool thing about modern karts, is that almost any kart from any major brand can be a player on-track. Find the brand supported in your area, and take your pick of your favorite color.
Like Freddy, I’ve been an OTK guy for the past several years and have really enjoyed the karts. They’re well-built, easy to tune, and fast out-of-the-box.
I would look for something used but not abused, make sure it’s straight and the rails aren’t flattened from going off-track, and go have fun. I would probably suggest something in the 30/32mm range if you’re running a heavy class, although a standard 30mm might work in a lower horsepower application like Yamaha.