Assuming your basics are all up to scratch ie arithmetic and basic geometry I would say the best bet is to make a start on the notes. Are you going full time or D/L. If full time I'm sure if you paid they would send you the notes in advance, if D/L then it doesn't matter when you 'start' so you may as well get the notes now.
Other than that I suppose you could read a met book or swot up on gyros/engines/any other topic but you won't really know what's relevant unless you are looking at something prepared with the syllabus in mind.
If you aren't ready to cough up then try and buy second hand notes for any of the tricky subjects ie instruments, met, performance, A/C Gen. (Only a suggestion before the usual 'i found that easy' argument starts).