If you want to wear a kilt feel free to wear it, fine by me. But as mentioned above kilts are a recent invention, I don't know my history but you may want to wear a belted plaid or the like. Once you see a kilt you'll understand that there was no way the highlanders of the 14th century were running around in them, way too intricate and 'fancy' for that time or circumstances.

Good luck in your RPG and welcome to the forum, there are several re-enactors around and they should be good sources of info for traditional garb.