Personally, especially if you say your congregation is laid back, Id keep it toned down. You seem to have many choices and combinations so you are flexible. Unless you are just tied to a PC or coat you might keep it to a nice button down shirt, tie with colors that compliment the kilt hose or a stripe in your tartan, waistcoat. Personally Im a brown leather guy and dont really care for the big shiny buckles but I do like the Thistle. Wingtips would do better than the brogues in my opinion, the brogues are fine for full blown dress up or games. I think the leather/fur sporran would suffice nicely also. Nixes for me would be white shirts, ecru hose, brogues. So that leaves you with claret and black. Depending on shirt choice, you say you have claret, you can use the black hose and the flashes. I think claret shirt and hose may be much, let others advise you on that, but if you go with claret hose, id chose a different shirt. This advice many be clear as mud, Im no expert but I do remember what I wore the first wedding I attended kilted and now just laugh at it. I like, as many do here, to mix the colors but in a way that shirt, kilt, tie, hose compliment each other... And if it is a relaxed atmosphere where you worship, id dress relaxed too.... Just my two cents that can be taken as that and torn apart by others as they see fit.....