Check out this thread
This thread should give you some visual ideas of what everyone is talking about. It has two series of pictures showing different levels of formality. I think that #6 and #7 in the first series is what you are looking for. Images #6 and #7 in the second series are also good for what you are looking for.
Here in the U.S. a darker jacket will likely work better for the semi-formal look you want so a dark gray or black tweed might work well if you don't go with the argyll. If you wear a sporran, go with something black to add to the formality, but you wouldn't have to get something with fur or silver accents if you don't want to or it is out of the budget. And a hat isn't really necessary if you don't want to wear one.
http://www.xmarksthescot.com/forum/f...-attire-46888/
The hielan' man he wears the kilt, even when it's snowin';
He kens na where the wind comes frae, But he kens fine where its goin'.
