A couple of rough route-maps.
The first shows the logical route from the town of Perth (and has written details of how to get to Perth from either Glasgow or Edinburgh airports). At Perth ignore signs saying "City Centre" and follow the ring-road and any signs for The North, Pitlochry, Dunkeld or Inverness, or any combination of these. This will get you on to the A9 (north), and from there you follow the map.
The other map shows several variations of the two basic routes (as above). Logic and speed are abandoned in favour of more scenic landscapes, and depending on how often you stop to take a few snaps, any of these could spill over into a second day. And it has to be said that most of the "logical" route has pretty good scenery too.