I just join random regionals, or worldwide if someone's in a different region.
As for the vehicles, it helps to know what some of the stats mean. Acceleration only shows an increase when it's raised by a whole number, so, for example, 3 accel and 3.5 accel are the same, it has to get to 4 before it would be faster. Accel is the only stat which works in this manner. Traction determines how far out you slide on drifts, as well as off-road speed. There are some terrains on some tracks that will make you slide more than on a road, such as the sandy or icy tracks, so traction will help more here as well. Also note that Blooper ink makes you slippery as well, and high traction will reduce that effect too.
Also, there are some hidden stats to consider. Lighter characters have better mini-turbo boosts than heavies, for example. With gliders, there are two types, the one with a bit extra accel and the one with a bit more weight. Accel gliders are faster in the air so they are typically the best, and weight gliders have more control in the air.