So may I ask, what would you do if you were me and you were to the highland games or a Celidh dance or similar highland gathering?
Highland games or gathering - tweed jacket and waistcoat or belt with leather day sporran. However, some games are very casual and in hot weather a shirt is sufficient with the kilt.
Informal ceilidh - the same as above.
Formal ceilidh - often black tie with a doublet or any of the black barathea highland jackets with silver buttons, waistcoat (no belt) and dress sporran.

Don't agonise too much. Wear what you have and enjoy the events. You will see all sorts of outfits at games and ceilidhs.

This site is a great source of useful information but since you will be wearing the kilt in Scotland, I would tend to go with the advice from native Scots as kilt-wearing conventions can be a bit different depending on where you live. Having said this, there are some very well informed and 'traditional' kilt wearers on the other side of the pond.