My advice....
Don’t go in the summer. Most of the country is infected with billions and billions of Midges (tiny biting flies that drive you insane).
West is best. Western Islands even better.
Wherever you go the chance of rain is high.
Don’t overlook the Scotland / England border area. Also don’t overlook Dumfries and Galloway. Both areas have great scenery, are relatively quiet and best of all have lots of great roads.
Visit at least one distillery, buy a bottle, open, throw away the cork and get roaringly drunk on it preferably sharing it with someone in the open air with a great view.
Campsites I would recommend:
Sunart campsite in Strontian.
Fidden Farm on Isle of Mull
Loch Broom campsite Ullapool
Sango Sands campsite Durness
Balloch O Dee campsite near Newton Stewart
Galloway Activity Centre and camping, near New Galloway.
Any of the campsites or wild camping spots in or near Applecross.
Countless wild camping (free) spots all over Scotland.