Hi Elaine! We're going to be in Scotland for two weeks in March! As you do your research of places to visit, especially the historical & heritage sites in Scotland, you may want to estimate where you plan to visit and then consider buying the Historic Scotland Explorer Pass. Given what we want to see/do, we bought the 14 day pass for roughly $43pp . . . less than 1/4 of the price of what it would be if we paid ala carte as we visited sites in their portfolio. When we were in Scotland back in 2006, we made great use of this pass as many/most of the premier castles are part of this organization (Edinburgh, Stirling to name a couple).
Be advised, there is ANOTHER heritage group (Heritage Trust of Scotland) with other properties, also of great historical interest . . . including castles, abbeys, etc. They too offer an explorer type pass for visitors, but you can save even more money by joining another similar organization that shares reciprocity for visitors, free of charge as a benefit of membership. We bought the American version (National Trust for Historic Preservation) for $30 (family membership). That will get us into all of the properties within the Scottish Trust for free. Ala carte, the price would be around $240 . . . and if we were to buy their visitors' pass, it would be around $94 for the two of us.
It takes some work but if you are traveling within a budget, this will no doubt save you some money! Feel free to write me privately if you'd like. I'd be happy to share with you my research & spreadsheets.