I'd suggest you go for the hard ones straight away. There are subjects like COM/HPL/PERF/OPP/AIRLAW which you will get done easily. Then there are subjects like INS/GNAV/RNAV/ASP/POF. I really suggest you take a look in those ones, or at least go through the CBT of them if you got it. You will have a relative easy time if you already have a good understanding of these subject in your later studies. Unless, it can become extremely stressful, (of course) depending on how much time you have.
Good luck
