Argyle jacket in black or charcoal, with a matching waistcoat. Black leather ghillies or brogues, and black leather or perhaps grey fur day/evening sporran (one without the silver cantle). Flashes. White shirt, turn down collar. Tie and kilt hose selection depend on the kilt you will wear.

Prince Charlie coatees, doublets, bow ties, plaids and brooches, jewelled dirks, etc, are only appropriate for evening wear.

Brown leather and tweed Argyle jackets, while often listed as daywear, are not ultra formal. If the group is following everything to the T, then stick with the black leather and the black or charcoal Argyle. If they are a little lax, you might be able to get away with the brown leather and tweed.