Hi Unknown_92.
You can tell how well prepared you are by considering your accuracies on individual practice questions and your streaks of practice q
uestions answered correctly in a row.
For example, if your Quant practice accuracies are around E - 90%, M - 90%, H - 80%, then you're likely ready to score Q49 or Q50.
If you want to score V40+ in Verbal, then your practice accuracies should be at around 90% for medium Verbal questions and 80% for hard Verbal questions.
Also, if you are getting questions correct in long streaks, such as 20 in a row correct, then you're probably ready to score in the mid 700s on the GMAT.
The upshot of all of the above is that you don't have to emphasize practice tests in your GMAT preparation. Of course, it's good to take some practice tests, but you can tell how you're doing by considering your practice question accuracies.
Also, for some tips on how to practice for the GMAT for best results, see this post.
The Best GMAT Practice Methods