I started with the same three in the same order.
After that I did
Performance & Planning (because it's easy),
Navigation and then
Aircraft (General)(actually doing that tomorrow or Saturday

- edit: done it and it was easy

). Final one will be
RT Theory which will get done just before I start on the Nav trips....
I'm happy with that order, but I'd move RT Theory before Aircraft General if solo Nav trips were sooner. RT is actually useful whereas Aircraft General can be done anytime and is boring as hell. At least it's reasonably easy....