Travellodge hotels are cheap and if you book them early enough they cost about £19 a room! The hostels are good as well with double rooms now.They even have castle turned in to hostels. I think historic Scotland sell tickets for unlimited entry which will save you in the long run. A middle sized car would be best and get the book Desire Lines by David R Ross as it will take you places not mentioned in other travel books.Mind you the best way to get about is a Motorbike with a tent on the back mind you that's just me(lol) All the places you mention are easy to get to from Glasgow or Edinburgh. hope this helps