Your final test as in your End of Course exam (EOC) or your final test as in you filled in the bubble sheet after answering the multiple choice questions in the CDC booklet? If it's just the one in the book, then that doesn't really count for anything other than a gauge of how well you studied the material/looked up the answers, so your supervisor knows if you are ready to go to the education office and take the EOC or not. If it was your EOC, and you have two actual sets of CDCs with two EOCs, then definately study harder for this next set, and then start studying whatever you want.
There's a reason that most shops won't allow you to pursue additional education until your CDCs are complete. They may seem boring, and even pointless to your overall career goal, but they do help you to know more about and to do your job now. If you don't excel at your current job, your leadership will be less willing to help you pursue your commissioning. As far as I remember you need reccommendation letters and such, and if your only a mediocre performer-or have the appearance of one, your commander will be less likely to endorse something like that. If you shine on your next EOC, the commander will remember your name for that when you gives you your day off, and if you continue to go above and beyond, people will continue to know who you are, making those letters easier to get.
Oh, and remember, CDC's are actually part of studying for Staff too... Just one NCOs viewpoint... PM if you've got questions.