Hi David,
A 520 is a solid initial CAT Score (the average Score on the Official GMAT hovers around 550 most years). Many GMATErs spend 3 months (or more) of consistent study time before they hit their 'peak' scores, so you have given yourself lots of potential study time too - which is good.
You should plan to take practice CATs/mocks at regular intervals (at this point, that would be every 2-3 weeks; further along, it should be 1 a week). After you've taken your next CAT, you should post back here and we can discuss the results and how you might adjust your studies going forward.
Beyond that data, it would help if you could provide a bit more information on your timeline and your goals:
1) What were the Quant and Verbal Scaled Scores for your first practice CAT?
2) When are you planning to apply to Business School?
3) What Schools are you planning to apply to?
GMAT assassins aren't born, they're made,
Rich