I took the series 7. Congrats on your job, I really enjoyed working for a brokerage.
I was having trouble passing the practice exams until my uber-boss gave me this advice:
Don't try to read through and master the material beforehand, then take the exams cold without referring to the texts. Maybe you might want to do that once or twice, just to become a little familiar with all the new information you have to learn.
What you do is take the practice exams, and once you get to a question you just can't answer, look it up in the text. Don't feel bad you didn't know it, but be sure to learn what you look up.
Do about 7-8 of the entire practice exams with this method, and you'll start to get passing grades. I studied for 3 months my way without ever passing once. After 2 weeks of studying his way, I was passing and passed the REAL exam on the first try.