Got 765 on GMAT Focus 2nd attempt: honest advice
Overall recommendation:
Grind as many practice questions as you can, without neglecting any of the 3 areas - even if one of the areas is a strength for you (getting your score up to 100th percentile for one section can seriously boost your overall score and is worth the effort).
Use the official mocks above unofficial sources as a primary indicator for your performance. I scored 725-775 on my last few official mocks, but I never got above 665, for example, on Magoosh
Use structured resources to guide you for the quant section. This post links a few. There is a huge variety of questions for the quant section, and knowing the tips and tricks is genuinely very helpful. I was skeptical of this method of study, preferring to rely on my conceptual understanding of maths and my ability to problem solve unseen question types on the fly. While these are necessary skills - and you should practice them - they are not sufficient. Structured resources took me from a 70th percentile on my 1st attempt to a 100th percentile quant score on my 2nd.
My study approach:
2 months of study before my first attempt, 3 weeks between 1st and 2nd attempt. Only really studied on weekends (~6hrs each Saturday & Sunday) for the first 2 months. In the last 3 weeks (between 1st and 2nd attempt) I increased to also study about 1 hr a day during the week.
I didn't buy any of the expensive USD 250+ (some $350+) courses (TTP, Magoosh, etc.). Instead I followed the main advice I had received - which is to just grind as many practice questions as possible. For this, I bought the official question packs and all the official mocks (did these under test conditions). Plus, I found this free question bank from Manhattan Review. I also followed some free online structured courses for the quant section (recommendation 3 above).
My background:
I studied Maths and CompSci in my undergraduate, and I am a home language English speaker.
My preparation experience:
Verbal: Surprisingly for me, the verbal component of the exam was always the easiest (getting 100th percentile on all official mocks, including my first one). But this overconfidence caused me to neglect verbal. I got 98th percentile on my first attempt at the GMAT focus - lower than all my mocks, dragging my overall score down substantially. After that I bought the official verbal practice question pack and worked my way through them, and got 100th percentile on my second attempt. The lesson here is to be sure not to neglect your strengths.
Quant: Another surprise for me, despite my quantitative background in university, I really struggled initially at the GMAT (70-80th percentile in my early mock tests). An unlock for me here was to also use structured preparation on top of question banks. For this I followed some free online structured courses for (see recommendation 3 above).
Data: Honestly nothing fancy here. I just did the question banks, and consistently got ~84. Perhaps someone in the comments can give advice for this section. I got the sense data was more of a time crunch where practice was the key driver for performance. Unlike the quant section nothing here stood out to me as needing structured support.