I would suggest that you take a look at the Show us your pics page there are both a formal thread and a dressy thread where members have posted pictures.
It might be a good place to start.
Here are the links:

Formal
http://www.xmarksthescot.com/forum/s...ad.php?t=22433

Dressy
http://www.xmarksthescot.com/forum/s...ad.php?t=22432

I would say if you are going dressy you can't go wrong with an Argile Jacket, semi dress or dress sporran, white dress shirt with french cuffs, cufflinks, and a tie, kilt hose, flashes, sgian dubh, and a kilt pin. You can most likely rent all of the above if you need to. Good luck with it and remember to post pics when you can.