IMHO, buy the best hose you can, oatmeal or grey in colour. These colours will go with any tartan. As to shirt, try to match a colour in the tartan or white, black or grey. Again, you will usually avoid a glaring clash using them. Following are some examples.

White shirt with oatmeal hose, Maple Leaf kilt.



Blue shirt with grey hose, "Blue Meanie" camo kilt.



I hope this was of some help.