If you were making a trad knife-pleated kilt in wool kilting tartan, it would be typical to have pleats that are about 3/4-7/8" (i.e., the reveal would be 3/4-7/8"), with a depth of 3.5-4" (reflecting a typical sett size of 7-8" or so. That way, you can get enough tartan into a kilt to give it enough weight to swing well.

So, if you have comparable plain fabric, I'd aim for depth of 3.5-4" and a reveal of 3/4"-7/8" if you want to have a kilt that looks traditional.