I am sure you will you get different opinions from different people about this question, but I can give you my recommendation.
After you have done a good job at reviewing the MCAT content I would recommend that you take about 2 or 3 practice test. Once you do that go over the exam for all of the questions, even the questions you get right. The reason is that you can sometimes pick up hints for questions in the explanations. Then I would review the content for the questions you got wrong.
After you review the exam and content take another 3-4 exams and repeat this process all over again and do a few free standing questions after you review a particular topic. Most MCAT books have this at the end of a section.
In total I would say take about 8-10, but the more the better. Just make sure you review all the questions once you finished, which is more important than just taking a practice test because you never know what kind of question you will get on the actual MCAT. Ultimately you want to score somewhere near your target score on a practice test.
Definitely make sure you do the AAMC practice test, because those are the best representation of how the actual MCAT will be.
Hope this help! Good luck with the MCAT. 🙂