Spanish Subject Test

I’m a junior in Spanish II (yeah, I started late), and I’m driven to take the Spanish subject test next year. What score can I realistically aim for, given that I’m able to spend between 1-2 hours on a daily basis preparing?

I took it last December and got a 630. My background is self-study and having lived in Mexico for a year and only speaking Spanish. I never took any classes and i am not a native speaker. I studied for one month before the exam with a used Barron’s SAT II Spanish study guide that I picked up on Amazon for $6 shipped. My first full-length practice test I got a calculated 510, but then the next tests I consistently scored in the 650-660 range. I honestly thought I would get a higher score on the real exam, since it was exactly the same as the practice tests. A lot of the multiple choice questions used the subjunctive tense.