May not need much. I'm sure some saddle soap will clean it up. And some leather conditioner afterwards (I use Lexol on mine), applied periodically, to keep it from getting too dry. I'd avoid using leather polishes/waxes, or any conditioners with wax in them. That'll just clog the leather, and defeat it's usefulness for stropping.
If the belt is any other 'color' besides natural/tan (vegetable-tanned or bark-tanned), like black, etc., it may or may not work as well as true bare leather. Sometimes the tanning or dyeing methods for 'colored' leather will strip many of the natural silicates from it, or otherwise cover/coat the leather. Same holds true for some cheaper belts that may be coated in wax/plastic material.