Although doing them in sequential order seems the logical way to do it, there may be some alternatives. If your maths is OK you could conceivably start with Exam II, but ideally you would want to know something about bonds and bond convexity and options and option gamma. But you certainly wouldn’t need to know Exam I material in detail. You could probably do Exam IV out of order as well, assuming that you have a reasonable understanding of financial markets – although once again you wouldn’t need to be conversant with the Exam I instruments and markets material in detail. I certainly wouldn’t start with Exam III. But I could envisage doing Exam II and Exam IV in any order, followed by Exam I and finally Exam III. But this would assume that you have a reasonable familiarity with financial instruments and markets, even if is not quite enough to pass Exam I, before attempting II and IV. The reason you might want to do it this way is to get some “runs on the board”. There is quite a lot to get through in Exam I and depending on how much knowledge you have to start with, the effort required might discourage you. But if you do II and IV and pass them, it will provide the incentive to knock over the other two exams.
Jim