I would recommend taking one of the GMATPreps up front to level set where you are. If you search here a bit you'll find that they're considered to be the best simulation of real exam difficulty.
If the first GMATPrep confirms your expectations, you can do the second on your prep home stretch and validate that you're ready to go. You can do GMATPrep multiple times, but I believe they lack a deep question bank and will start to repeat. This will obviously inflate your scores and reduce their predictive value.
As part of your core efforts, do the OG questions above all else. I never made it to the additional OG guides. I did do Kaplan 800--it wasn't perfect, but I did get some value out of it. I would do small sets of questions from K800 before bed and sleep well if I was handling them well. I wouldn't feel obligated to spend the money on this book, just buy the OG and consider the 2 online resources listed below. If you're not progressing to where you want to be or want to do an extended prep cycle, you can go back to these and other sources for additional content.
The
Manhattan GMAT CATs can be bought online for a $20-ish, you can use those as additional CAT work during prep. They typically score lower than the actual GMAT but they're good learning tools and considered the next best thing after GMATPrep.
Additionally, I also did the
GMAT Club Tests and they're an excellent source of practice content. You can take the free sample tests to confirm that for yourself.
As far as comprehensive books, I hadn't seen the business end of an inscribed triangle in quite some time, so I did get value out of doing math review (I worked through Manhattan's Study Guides and Jeff Sackmann's GMAT Math Bible along the way). Manhattan's SC and CR guides are also pretty good imo. If you're current on the math basics used for Q., then proceed directly to the OG. Otherwise, focus on making sure you have the common question types down. The good thing about guides like the Manhattan SG's is they spell out the likely universe of question types you're going to see, so you're not inferring some sort of taxonomy on your own.
I can't say which approach will work better, but I think after you do a practice test, you'll have a sense of whether you need foundational coverage or can go straight to focusing on whatever level of practice reps you feel you ned.