My personal opinion of a good order would be:
Air Law . .Communications + RT Practical (better do this asap, as it will pay benefits through your flying training - less you worry about the R/T, the more you'll learn during a lesson :-) ) . .Navigation/Radio Aids + Flight Performance/Planning + Meteorology (as these are tests of the practical skills you'll need for the later stages of flying training) . .Human Performance + Aircraft General (as these are tests of knowledge that will only be really useful once you have qualified, but not much use before)
When I was studying for the exams, I studied most of the subjects at the same time, as they tend to reinforce each other and I wanted to pass them quickly (so it didn't hold up any flying training). I still get the books out and refresh my memory on a regular basis though.