I am also this Question ?who can help me in math test ?
Depending on your starting level you might need more or less study material; even before that, thou, you might start exploring the Gmat Club and the quantitative section.
If you are following the OG12
you might look up answers explanations here and then figure out you weaknesses and strenghts.
Basically everything you might need you can find it here, including theory:
For example math-number-theory-88376.html
There are a lot of great guys here who might help you.
"The Burnout" - My Debrief
Kudos if I helped you