I'll second the advice on making sure the kilt fits well first, and wearing it at the appropriate level (natural waist for a traditional kilt, not down on the hips like trousers). When sized and worn correctly, a belt should not be needed for most body types.
If you do choose to wear a belt, the buckle type will really depend on the belt itself. Most commercially-sold kilt belts don't have holes for a buckle with a prong or tongue to go through. They just fold back on themselves, sometimes fixed with velcro or some-such, and the waistplate of the belt hooks into a metal clip on the other side. This is more of an evening-style belt, though there are some variations of them that are more suited to daywear.
So the first question is what type of belt you're looking to put a buckle on. Not every kilt buckle can go on every kilt belt.
Kilt belts are usually 2" to 2.5" wide (I think 2.25" width is the norm but don't quote me on that); they are much wider than typical trouser belts. Wearing a narrow trouser belt with a kilt looks ...odd. So again, depending on the width of the actual belt you're looking to put a buckle on, it may limit what you can actually use.
I rarely wear a belt these days with a kilt, but of the belts I do have, I much prefer a daywear belt to look decidedly different than an evening/formal belt. This waistplate is of the rectangular variety, but its shape and material/finish are more suited to daywear IMHO, as opposed to a shiny white metal rectangle.
*edited to add:
You can also go more non-traditional with something like a military web belt. The width is just right for a kilt belt, although it is definitely in the "out there" category. I haven't been arrested yet for wearing it with a kilt.
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