While I am not a piper, I have seen many competing pipers over the years. I have yet to see one wear anything less than a full 8 yard heavyweight traditional worsted wool kilt. Mr. Cajunscot and the others have listed some excellent kiltmakers. They would certainly be qualified to advise you and outfit you in the appropriate fashion. Do it right the first time. Be prepared to open your wallet... but you can be confident that it is an investment you will never regret making. Being dressed well and correctly can only add to your confidence in the circle.