The CR Speed belt is sort of the standard in USPSA competition.
CR SpeedBut Safariland and Gugas Ribas makes the dual system belts too.
The CR is around $50.
Several competitors use one inner belt and get 2 or 3 outer belts for the different divisions they compete in. That way they can leave all the division specific gear on the belt and not have to swap everything out when they change divisions.
Of course you can use a good leather belt, but they're gonna be the same price or more and they're not as convienient to 'ungear'.
Hope this helps.