Good question - there are a few things I'd recommend in order to improve on specific areas:
1) For math concepts like "exponents", there are additional skill-based questions and explanations in the Math Essentials (Lesson 0) book and On Demand lesson. Often times you'll find that the On Demand lesson adds a few of its own examples to help accentuate those topics.
2) You'll find additional subject-specific questions and feedback in the Veritas Prep Diagnostic Quizzes available through the Practice Tests link on your TrueTrack account.
3) To truly test whether you've mastered a concept, I highly recommend taking the questions that you've already completed and rewriting them on your own - tweak a variable or term to elicit one of the other answer choices. That helps you to understand each question from multiple angles, which is hugely helpful on a test like this.
4) You can find additional math subject-specific drills and conceptual help at websites like http://www.purplemath.com;
there are quite a few free math resources available online for teachers and students to develop those skills.
I hope that helps!