If you dont have a lot of time to visit the country, I reccomend a 3-days trip around the Highlands. They are the heart of Scotland, and I think it's something not to be missed. The landscape is always amazing (postcard-amazing!), and in a short time it's possible to see a lot.
I bought a 3-days trip that started from Edinburgh, to Stirling, Perth, Forth Williams and Loch Ness. The coach took frequent stops, so you don't really feel the long drive, and you see so many amazing new things that you forget about the travelling! Usually the guides are very nice and funny Scots, and it's also a good opportunity to make some new friends since usually the people who take these trips are in their 20s...
Do bring an umbrella!