GMAT in 30 days - help!!!

What were your subscores for the quant and the verbal? How did you prepare the first time? Were your practice scores closer to the 500-range before you took your first test? Or were they higher or lower?

If your practice test scores were closer to the 500-range, then it may be challenging to improve by 150 points in 30 days.

If your practice test scores were actually higher but dropped for some reason on test day, then it is important to try to figure out why your score dropped a lot on the real test, so that you can take the necessary steps to minimize the chances of a similar score drop when you take the test again.

What materials are you using to teach you the grammar tested on the exam? (I assume the Princeton Review book you mention is teaching you the math content you need to know.) What about strategies for handling the different questions types or content areas?

I'm not familiar with the Manhattan Review materials, so I can't tell you whether to use those specifically, but you do need some resources for things like: grammar, general SC techniques, CR techniques, RC techniques, DS strategies, and possibly techniques for various math problems / content areas - for example, how to translate words to math, how to use real numbers on theory problems, how to simplify / find shortcuts on all kinds of math problems, etc.

If the books you already have give you these things, great - use them. If not, you may need to identify additional resources.