By official material do you mean verbal and Quant review books??
I should have been clearer here. I just meant that you want to make sure you're doing the official practice exams as part of your study regimen. The quant and verbal review books are a bit outdated, so if you were to need additional practice problems, the Question Pack from mba.com would be a better resource:
https://www.mba.com/us/store/store-catal ... ack-1.aspx
Philosophically, I agree that quality is better than quantity. Given the choice between thoroughly dissecting the Official Guide questions, and feeling as though you're haphazardly making your way through too much material, the former is clearly preferable. My advice for now: start working with the material you have, and you can revisit the question of whether the Question Pack would be beneficial at some point down the road.
Also doing 1 test per week without even completing the material would not reflect true results since it will take atleast 2 months to go through the material and last month to be kept for testing.
True enough, but the purpose of the practice tests isn't really to derive "true results." (At least not until the last couple of tests when you'd like to see that you're within striking range of your goal score.) The purpose is to master the timing/format/strategy of the exam. For most test-takers, this takes some time. What you'll find is that the GMAT isn't really a content-test, per se, but rather, a test that requires a good deal of creative and fluid thinking under pressure. Many questions will require no math knowledge at all. Like any skill, it will improve with practice. But everyone's different. There's no magic number for how many practice exams you should take. I would say that for the majority of test-takers, it's a good idea to take an early practice test to get a benchmark. (Your study plan, if that first test is 720, will be drastically different than if that first test is 540.) And then, at some point, you want to be taking tests with some consistency to master the strategies and timing, while giving yourself adequate time to thoroughly dissect the last test you've taken. On average, in my experience, that comes to about a test a week, but I've seen extremes on both ends. I do however, think it's reasonable to give yourself a little foundation-building time before you start regularly taking practice exams. Whether that means starting in one week or 3-4 weeks is up to you.
Most importantly, know that you can always make adjustments. It's possible that you'll work through your guides, whip through the OG, take a handful of practice tests and that you have time to spare. And it's possible that you'll hit some roadblocks along the way, and you'll want to take a few more practice tests and work in some additional material. There are many paths...
Keep us posted.