I agree with username123.
I feel like you're being too broad with the scope of improvement. You didn't mention the MGMAT Sentence Correction
Guide. I highly advice you to get that book and learn the material thoroughly since you can master the SC section easily with enough practice. As for CR, Powerscore is good. And RC, you just need to make sure that you're reading and absorbing the key content and message of the passage without wasting time on it too much. I've heard conflicting opinions, but I feel like the RC part is the one where you can actually get away with a lot of right answers without knowing too much of preparation as long as you ask yourself the following when you look at the passage:
1. What is the overall message?
2. What is the first para trying to convey? The second? The third?
3. What is the conclusion?
As for Quant, you can use the Number Properties Guide
from MGMAT if you have that or the OG12
. Just make sure you understand questions. Whether you get them right or not. And that should help. Use flash cards or something for concepts you don't know. If you have at least a month left, use the error log
Hope this helps.