(Maybe the mods can separate this out into a separate thread "Order to take exams in" or similar - so it's easier to find for the future...?)
Air Law and Operational Procedures are quite closely linked, combining them makes a lot of sense.
Most people apparently find Human factors easy so you can probably do it any time.
RT and Nav share a fair amount of syllabus and are probably best taken once you've done a bit of actual in-flight navigation, when it becomes clearer why things are done the way they are done.
Met is quite chunky and you may want to do it sooner rather than later.
The 3 technical subjects are all related and you may be well off doing them together.
I did mine in this order:
- Air law
- Operational Procedures
- Human factors
- Meteorology (Second weekend)
- Principles of Flight
- Aircraft General
Looking back, I probably should have done RT and Nav together and all the technical subjects together.
YMMV, though - you may find some subjects easier/more difficult and therefore wish to group them differently.