I wouldn't waste time on Reading Comprehension, it's very hard to improve in a short period of time. You get better bang for your effort by doing Sentence Correction or Critical Reasoning and use the extra time gain from there to compensate for RC.
Regarding the Quantitative section, you need to figure out what're your weakest topics then hit the books accordingly. Keep in mind that with very little time to prep, you can't hit up every topic so just aim for the best value for the effort.
I agree with mostly everything that deadlycat said; however, I am not quite sure about the recommendation to NOT spend (waste? hmm...) on RC. Maybe that's true for most (few?) native speakers, but I have known a handful on native speakers in this forum who had to work through some sort of strategies in RCs. Nonetheless, if you are a non-native speaker, then you MUST spend some, if not significant, time working on your RC strategies; otherwise you will realize it will KILL YOU in the test, not only with the time, but also with the accuracy - getting a string of wrong answers will hurt your score more than anything.
Regardless, whether you are native or non-native speaker, GMAT RCs are not like other CAT RCs. GMAT RCs are dense, convoluted and, perhaps, a big giant CR - at-least if you are aiming to score high, you would expect the complexity to grow. Moreover, the RC question stems expect you to stay within or outside the scope, at different level, for different types of problem. Not trying to exaggerate or scare, but I didn't realize all this until recently. It is so important to know what scope you need to be in while picking the answer choice for different types of problems.
Having said all the above, I will recommend to start with Powerscore Verbal's RC section, if RCs scare you in-general. I have read both Powerscore and MGMAT, and hats off to Powerscore for making things so much clearer. It does not give you ton of strategies, but teaches you for what you should be looking while reading a passage. MGMAT book
is more about attacking strategy, but Powerscore is more at the fundamental level, which is definitely recommended for non-native speakers, at the least.
Hope this helps