99th percentile overal, 99th verbal, 92nd integrated reasoning, 88th quant, 5.5 AWA
I spent 25 bucks on the Princeton Review GMAT prep book (GMAT 2017 Strategies, Practice & Review with 2 practice test) and studied for 2 days (while on spring break on a beach) and improved my score from 640 (practice test) to 770 (real score). Never studied or taken the GMAT before. I decided to apply to Harvard and Stanford's deferred program for college senior on a whim while on vacation and literally booked, studied and took the GMAT within that week.
I guess you don't really need to spend an outrageous amount of money to score well on the GMAT. I identified my trouble spots (Verbal section) using the practice test and then spent about two full days, 8 hours each day studying that section only. The Princeton Review book has multiple chapters for each section. I just divided the hours I have for studying equally for each chapter and try to hit that time target. On the test day I tried not to get too bogged down with any particular question, and was very cognizant of the time. I also recommend practice questions with graphs because sometimes they can give you some wacky bar/chart questions that people normally don't encounter and therefore do not know how to interpret the graph.
I was nervous to take the test, and also did not take a second practice test after the first one (I only had a couple days to study so I could not realistically take a second practice test).
For people like who are pressed with time and doesn't think they have enough time to study for a good score, go for it! Also, it helps to be a senior in college where you are still in studying mode.