Depending on the weather you'll route east or west (pretty rare you get to fly straight up the middle!)
West coast Cumbernauld then the Great Glen, Inverness or Wick (both HIAL) and with basic catering & fuel) then to Tingwall which is the obvious base.
HIAL operate most of the 'municipal' type airports. They are an inefficient generally worthless bunch who consume close to £20M per year. But on the plus side landing fees are usually less than £20. Fuel - check on hours of availablity. They are big on beaurocracy so apply for the 'out of hours exemption' Which as you may guess allows you to use their airfields out of hours!
On the East coast - Fife has fuel and good food, Perth is pleasant with fuel but food is pretty limited.
The expertise for the out islands comes from the Direct Flight chaps at Tingwall - they will sell you Avgas but brace yourself 'elf and safety' amongst other things makes fuel pretty pricey.
Whilst you are flying past don't neglect Orkney - probably more tourist value (ducks!) and a good bolthole so long as there is no fog around (Grimsetter is pretty notorious).
Onve you get clear of the central belt the world cheers up, controlled airspace where present is easily transited and the scenery (but also unfortunately also the weather) gets a whole lot bigger. So take your time and enjoy the view (and always have a plan B!)