I'm in the same boat amateur. Im using the AFT texts, im finding they are really good- tho i do agree i think systems and flight planning are going to be my downfall. I also have Avery's flight planning which is really good - very straight to the point and easy to digest. Though i would be wary because he does round off to0 much as i think someone said before. One thing ive noticed between AFT and Avery's FP text is that they actually provide conflicting information on what and where and how to round. I think i might stick with AFTs method.
Good luck!