Assuming your basics are solid, I would go through the entire OG, Quant and Verbal, and the Advanced Questions 2020. Ideally do the OG questions in sets of 20 and gradually speed up over time. The beauty of going through the OG is it highlights areas in which your basics are lacking and you can focus study those topics and come up to speed. Concentrated practise in difficult areas helps drill concepts.
Keep doing the GMATPrep tests say on a weekly basis to learn time management skills. Once you are through the Prep Tests, do the 700+ and as many of the 600-700 difficulty Verbal questions on the GMATClub forum (use the tag function). If you are really strong in CR, skip them and just do the SC. At-least for me, SC can be a wild-card. GMATPrep questions are probably the most representative of the actual exam. The reason you want to do them after you finish all 6 exams is it would contaminate the results otherwise. Can't really simulate the stress of 36 questions in 65 mins if you haven't seen the harder ones before and breeze through them.
Increasing your verbal score to V45+ gives the most bang for your buck. But is also fairly difficult and somewhat luck based (IMO). 3-4 mistakes can land you a V45. 1 mistake could get you a V48. No mistakes for a V51. So it's pretty unforgiving. Which is where practising so much SC helps, as if you can be relatively fast with them, gives more time for the crazy technical RCs GMAC loves to throw at you.
The 1-1.5 month timeline is fairly tight, otherwise TTP Verbal is pretty solid. Definitely see all the GMATNinja videos on YouTube - they are phenomenal. I skipped the CR, but saw all the SC and RC ones.
Make sure to maintain an
error log. I have 2 word files (Quant and Verbal) with my errors and key learnings/random tidbits from mistakes collated. Typically go through it on the day before I give a mock. And will go through before I give the actual thing in 1.5 weeks! Best of luck