Hi orange1
There are a few ways in which you could go about increasing your GMAT score.
You could go the comprehensive route, in which you would seek to learn more about all aspect of the GMAT and thoroughly learn from the ground up how to answer all kinds of GMAT questions.
You could seek to drive your score up point by point by focusing on question types in which you are least strong one by one.
You could use an approach that is a blend of the above two approaches.
My call is that, given what you have done so far and your practice test scores, you would be best off using an approach that leans toward the first of the three, an approach like the following.
For quant, go through the two practice tests that you have taken and see what came between you and scoring Q51. To do so, consider the questions that you didn't get correct and why you didn't get them correct, and also look at all the other questions to see which you were the most and least comfortable answering.
After having done this work, you should have a sense of what you could focus on in order to increase your quant score.
For every type of question that you are not really comfortable answering, you should learn all about how to answer questions of that that type and then answer dozens of questions of that type, getting to a point such that you are sure that, if you see such a question on the actual GMAT, you will answer it correctly.
Given that you have scored Q46 and Q49, my guess is that by focusing on 10 question types in which you are not particularly strong now, you could get to Q51. That 10 would be sufficient is not guaranteed, obviously, but by becoming super good at answering questions of 10 types that you are not strong in now, you should make a huge difference in your performance, for two reasons. One is that, on future tests, you will get questions of those types correct. The other is that, when taking a test, you will answer questions of those types quickly, leaving yourself a lot more time to figure out how to answer any other questions that you see.
So, the key in quant is topic by topic practice, to drive your score up point by point.
OK, now for verbal.
In verbal, it appears that currently the sophistication of your approach to answering verbal questions is putting you in the low to mid 40's. However, people often score lower in verbal on the real GMAT than they do on practice tests, because in doing even a small amount of verbal training, people pick up on patterns that they can use to answer practice test verbal questions but that don't work for answering questions on the actual GMAT, questions that contain new twists. So, since you want to score 750+ on the GMAT, you have to make sure that your approach to answering verbal questions is sophisticated enough that you will score at least 41 on the real test and, hopefully, higher.
So, what's the approach to use?
You could do the following.
Getting verbal questions correct is a matter of what you know, what you see, and what you do. So, your next move could be to go through your practice tests and, for any verbal question that you didn't get correct, ask yourself what you didn't know, what you needed to see, and what you needed to do differently in order to correctly, rather than incorrectly, answer that question.
Armed with that information, you could then do verbal practice questions, slowly and carefully, seeking to see what you have to see and do what you have to do in order to choose the correct answers rather than tricky trap answers. You goal should be to answer all practice questions correctly and to refine your approach. So, practice SLOWLY. There is no point answering them incorrectly in two minutes each. Just get them correct, and for EVERY CHOICE in every question, seek to define EXACTLY and thoroughly why that choice is incorrect or correct. The point is to learn to go well beyond choosing what sounds right to using sophisticated, logical reasons for making the choices you are making. You need to develop skill in defining why choices are correct or incorrect. Only by doing so will you consistently score high in GMAT verbal, in which the questions are full of tricky traps.
Once you have worked on a bunch of quant question types and improved your verbal skills significantly, you can take another practice test to see where you stand. If you spend around two days per quant question type and do some verbal work at the same time, you should have made great progress in a few weeks. If you don't hit your score goal comfortably on that next test, then continue in the same way, topic by topic work in quant and thorough, careful answering and analysis of verbal questions. With that type of work, you are pretty much guaranteed to hit your score goal efficiently. If somehow you are not seeing the results that you want, you can come back here and get some ideas on how to adjust what you are doing.