Hi,
I have taught many students over the years who have prepped in 1 month, though my first choice would to be to advise more time if possible. But nevertheless, I have seen plenty of success in a one month timeframe, it really depends upon you--what your current skill level is, and how much you put into it this month.
It's best to take an initial practice test to really diagnose what you need to focus on the most and how to prioritise. Then you'll want to plan out your month in detail, aiming for 1-3 hours/day, 5-6 days/week at least, perhaps longer sessions on the weekends. Aim to complete 4-6 CATs or therabouts during the month, spaced out approximately evenly. Spend time reviewing each CAT that you take (something many people neglect to do, to their detriment). Review the content you need to (math and grammar), focus then on strategies and timed question practice, and ensure you get sufficient computer-based practice. Let us know if you have more specific questions!
Jen Kedrowski
Kaplan Test Prep & Admissions
GMAT Teacher
MBA Admissions Consultant
National Product Team Member