Hi Accountingg,
Raising a 400 to a 650 will take some serious work - and you'll have to make significant improvements to how you handle BOTH the Quant and Verbal sections. Thankfully, the GMAT is a consistent, predictable Exam, so you CAN train to score at a higher level. Based on what you've described about your studies so far, there are some immediate adjustments that you have to consider:
1) Many Test Takers spend 3 months (or more) of consistent study time before they hit their 'peak' scores, so it's likely that you just have not put in enough time and effort yet. Studying for less than a month would have limited your progress - and it's unclear exactly how you were studying during that time. Working through random practice questions isn't an effective way to prepare for this Exam.
2) It appears that you tried to spend no money on the preparation process. Considering the importance of the GMAT Score to your application(s), possible scholarships and possibly your career (some companies actually ask for your GMAT score during the hiring process) - you have to look at this whole process as an investment in your future (and not as a series of expenses to be avoided). This is meant to say that your 'big picture' plans could be completely derailed if you try to approach all of this with an emphasis on doing it cheaply.
1) When are you planning to apply to Business School?
2) What Schools are you planning to apply to?
GMAT assassins aren't born, they're made,
Rich