Only way to go. Studied the material for the 55 and took the test without bothering with the practice tests. Did not take it seriously. (I had a "grandfather" exemption for whatever it was...2 years if I remember).
Did not pass.
Second time, just did all the practice questions and passed with an 85. Understood hardly any of it. Didn't care, didn't matter. Just know the answers and forget about why they are what they are.
Thing about the 55 (I have heard it's changed somewhat since I took it a few years ago)....none of it makes sense, and none of it matters to us. So it's just remembering if the answer is 90 minutes or 30 seconds, etc.
A total waste of time, but the rules are the rules. Can't trade without it, so just memorize the questions and answers and don't even THINK about the "whys".
Series 7.....maybe sometime you may want to know some of the material. Or have use for it. Series 3 a MUST if you want to truly understand commodities. But the 55? Our operations gal who actually did the stuff failed the first time (she too did not study).
Practice, practice, practice. (Do it one night before so it's fresh in your mind....don't make it to be like the 7 which actually takes weeks to learn).
Peace,

rs7