Applicants must find their own ways to prepare for the GMAT, since different applicant has different profiles, with different strengths and weaknesses, as well as different timelines and money to spend. A great place to see a lot of information about the GMAT, including the experience of different applicants of different profiles, is the GMATclub forum.
I can tell what worked for me. I found very early that I needed much more preparation for the quantitative section than for the verbal section. I read a lot of texts in English (books, magazines, comics, websites), and have been doing that for decades now. I think that prepared me for a lot of verbal questions. So, I spent much more time with preparation for the quantitative section.
In order to prepare for the quantitative section, I strongly suggest you the Manhattan GMAT books. They may be expensive, but they are really great. They helped me to recover my mathematics skills, know about GMAT questions, and develop a strong foundation.
The Official Guide for GMAT is another essential book to prepare for the GMAT. But, to use it alone is not the best way, in my opinion. GMAT Prep Now is a free GMAT preparation course, which use the Official Guide. So, with GMAT Prep Now you will be able to study the Official Guide in a much more organized way, helping you to evaluate your performance, and it will also add several tips and strategies which are not included in the official guide. The Official Guide is actually very lacking in test taking strategies, its value is due to the quality of questions.
The Official Guide is not only lacking in strategies. It also does not provide many questions at the higher level of difficulty. Since you want to get a high score, knowing how to solve questions at the level found at the official guide is not enough. You will need harder questions. And the source of harder questions I found is again the GMATclub, with its question bank.
Following that path, I was able to go from Mathematics revision, to a general preparation for the GMAT, and then end with hardcore questions focusing on my those points which were still weak after months of preparation. I was able to improve from a total score of 600 (my first mock test when I barely knew about the GMAT) to 750 (my last official score, used in my applications).