(FYI - I think you accidentally bolded everything in your post. Might just want to check the settings next time.)
You are absolutely right that you don't want to take too many tests - or take them too frequently - but tests are also an important indicator of your strengths and weaknesses. Your results help you to know what else you need to study.
I recommend taking one practice test very early on - within a week or two of starting your studies. Analyze the results to help you prioritize your studies for the next several weeks. You can use the article below to analyze MGMAT CATs:
http://tinyurl.com/analyzeyourcatsIn our classes, we place the first practice test between classes 1 and 2 and the second one around class 7 (or about 5 weeks later). The third test is around week 9 (though I prefer after that class, so about 3 weeks later).
After that, we recommend a test once every 2 to 4 weeks while you are still in "trying to get better" mode. When the real test is approaching, we recommend switching to a "review" mindset for the last two weeks, during which you take one test a week (one test two weeks out and one test one week out).
Here are some resources on studying for this test, in case you haven't read them yet:
https://www.manhattangmat.com/blog/inde ... lly-tests/http://www.manhattangmat.com/blog/index ... -the-gmat/Finally, if you'd like, you can come back here to tell us what your study plans are. If you also tell us your strengths and weaknesses (based on your CAT analysis using the article I posted up at top), we'll tell you whether we agree and advise you further. (Note: do share an analysis with us, not just the raw test data. Part of getting better is developing your ability to analyze your results - figure out what they mean and what you think you should do about them!)