Firstly, if you like trail centres that’s fine, but they won’t be much different to the English ones. To really get to grips with Scotland and the real wilderness experience you need to do the natural stuff.
Completely agree with TJ that Aviemore is a great place to base yourself for up to a couple of weeks. Some of the best riding in the UK on the doorstep. Talk to the Bothy Bikes guys about routes. 30 mins to Laggan, an hour to Ft William. An hour to Golspie?
You definitely need a couple of days in Torridon – awe inspiring scenery and incredible riding.
Definitely get a couple of books and ping people nearer the time to get people to show you round.
The midges get worse the further west you go, and are forecast to be pretty bad this year. Get plenty of Avon Skin So Soft. If you’re spending that much time up there you can avoid the worst midge days when there is no wind