Hi Vazirani,
Many Test Takers are unhappy with their initial practice scores, but you really shouldn't be. Your 580 is actually a solid performance (the average Score on the Official GMAT hovers around 550 most years) - and it's just a measure of your skills right now. You'll improve on that result over time as you learn more about the content, Tactics and little 'secrets' of the Exam. That having been said, raising a 580 to the point that you can consistently score 700+ will likely require at least another 3 months of consistent, guided study - 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.
Before I can offer you the specific advice that you’re looking for, it would help if you could provide a bit more information on your timeline and your goals:
1) When are you planning to apply to Business School?
2) What Schools are you planning to apply to?
3) Going forward, how many hours do you think you can consistently study each week?
GMAT assassins aren't born, they're made,
Rich