The GMAT OG 13 is non-negotiable. If you want a 700+ score, you have to know what official GMAT questions look like. DOWN COLD.
For Quant, I think MGMAT Number Properties is a great book to start since this is not usually an area many students are familiar with -- beyond that it depends on your personal weakenesses: Algebra? Geometry? Word Problems? I usually suggest my students supplement with a combo of books from sources such as MGMAT or Veritas Prep and online resources such as GMATClub, BTG, Grockit, etc. It really depends on the student. GMATPrep is NOT one size fits all.
For SC, drop everything and get MGMAT Sentence Correction. That book used in conjunction with the OG13 and GMATPrep questions are ROCK SOLID. Just be sure you're approaching SC with solid strategy. That, combined with the content knowledge you'll learn from this books, will really set you up well for Verbal.
For RC and CR, it's tougher because you can't just memorize concepts. You know to recognize all the individual question-types, and learn how to break down a passage on your scratch pad and know what each specific question requires of you. You gotta build this thing from the ground up. Books will only take you so far. That said, I'm partial to the Veritas Prep RC book and Powerscore CR.
Here's 10 more general tips to help you prep for the GMAT in the right way:
https://gmatrockstar.com/2014/06/17/10-w ... this-year/
Hope it helps, Shyam! Rock on!