Take a mock test, decide your target score, see how close you are to that score then you can decide on the preparation. Do a self analysis on what topics you are weak, it is not enough to know which section you are weak, you should be knowing which topics say probability in quant, strengthen/weaken in CR are your weak areas. Once you dig deep down to that level you can workout a study plan. If you reach your target score in the mocks then your 1 month plan will work out very well, all you need to do is dust your weak areas and go for the exam.