I think a good way to start is thinking about what kind of jacket (fabric, color) you should wear when in pants.

If a tweed jacket is good with pants - for the situation - it is good (enough) with a kilt, too. The style must be different, of course.

If you should be wearing a waist coat with pants, you might wear one with your kilt, too. Otherwise you might not need one.

Most important, the color of your jacket (and waistcoat) should match the tartan of your kilt.

By all means, I should go for a jacket as universal as possible.