First of all: i know this sound's trolly, but believe it or not, I just didn't have enough time and/or motivation to do more. I don't know if it is helpful for others, but i think the density of my programme might give some conclusions about how to really quickly adapt to the GMAT. I will explain that in three steps:
1. What I did:
I took the first day getting an overview over the material. Knowing that I won't be abled to go through a lot of stuff, I decided to take the
OG and buy the
Manhattan books that would make sense for me as ebooks on amazon. I later also bought the GMAT writing pad from Manhatten, which I would buy earlier now, because it really makes you familiar with a slightly different writing feeling. I then first read almost the whole
Manhattan GMAT Roadmap. Quite good for some first impressions. I then took the
OG introduction test to get to know my problematic zones. Afterwards I took the first test and scored a 640. I read through half the mathematical basics Manhattan book or whatever it is called and realised i was mathematically prepared well enough (my study programme includes some advanced mathematics). A further problem was my sentence correction, so i bought the Manhattan SC book and read everything except the advanced sections at the end. I also had data sufficiency problems at first and hence decided to do a bit DS questions in the
OG. At a specific time, in the middle of the DS questions, i started to use the
OG Archer of Manhattan - that was really the best decision in my whole preparation. After taking some practice, i started doing some CAT's - that was probably the worst decision in my preparation. I think I took 3 CAT's and one only Quant test within 36 hours or so. That simply was useless. I really didn't actually check my wrong questions, but did tests over and over. Probably that even made me lose half a day. My results varied between 630 and 680 until I realised it was useless. I called back the success of using the Archer and started over again with that, sadly this was the day before the exam. So I did about 130 questions from the
OG that day (PS and SC). First some questions, then the second GMAT Prep exam (690) and then some questions again.
2. What I would change
If i were to take it again (and I am not sure yet wether I should actually do that, because in total I did 1/3 of the
OG questions and my quant differed due to concentration issues because of the programme's density between 38 and 50, so i think i could really step up to 730/740), I would even narrow the range of the materials down. First of all, i would try to take 3 weeks. I think it simply makes more sense, though imo 3 weeks are enough. I would start reading the Roadmap again, and then FOR SURE read all the Math books of Manhattan, SC and RC. I don't know the book but for CR i think it is hard to improve - either you can do it or you can't do it. I am a non-native speaker and scored for me quite well in the verbal, so I would put mor effort in the math, basically in practicing. Hence i would try to do ALL the
OG questions using on EACH ONE the Manhattan
OG Archer. I think it really has a good learning effect, as you can directly see what you got wrong and have the time and motivations to improve. When I did questions without it, i simply quickly overlooked the corrections of a question block. And I would probably also have a look at those official quant and verbal books. The GmatPrep was imo not so helpful, but the two CATs are great of course. I would probably do a CAT every 3 days, just to have a look where you are and what you have to improve. I think this is it. And i would not spend the last day with relaxing, but practicing some math again, so that you are really into it. I even did some questions (luckily I still had plenty left :D) on the test day, before the exam, just to be warmed up for the calculation stuff.
3. Concluding recommandations
You only have little time for the GMAT, but are free to work all day? Don't worry, you'll be fine! Take some days, reading the Roadmap, do the introduction test of the
OG and pick the
Manhattan books for fields you have to improve. Then simply practice. Use the
OG Archer or anything that makes your learning process like this: question - answering - correction - learning - saving the data - next question. I think this is actually THE best thing to do.
So thanks for what I've learned here and I hope this is helpful to someone.