I would have to agree with Jock less is more, and a very good thing to keep in mind as you go forward. Let me ask, what do you have now? Do you have a good quality day wear sporran? Good quality hose? and a pair of good quality shoes? If so you are well on your way to having a Traditional Kilt outfit. As Jock said a Jacket and Waistcoat would be high on the list, I would suggest as well as the colours Jock suggested that you look at a Charcoal Gray as well. I was able to get a Charcoal Gray Jacket and Waistcoat from a local tartan shop as they were having an ex rental sale it really helped keep it on budget. My Charcoal Jacket and Waistcoat remain my most versatile in my wardrobe. I would also say a solid colour tie, using one of the colours in your tartan is to my mind the best. Something like this



or this