Hi Rags95.
Since you took your first practice test without any preparation at all, it's likely that 330 represents a skill level somewhat below your current actual skill level, since you weren't even familiar with the types of questions that appear on the GMAT when you took that test. So, it's possible that your actual skill level is closer to 400 level.
Even so, it's likely that you'll need more than three months to get to 700+.
Typically, people who start in the upper 500s or 600s take about three months or more to learn everything they need to learn and develop the skills they need to score 700+. People who start in the 300s or 400s typically take longer than three months to get to 700+. In fact, going from the 300s to the 700's typically takes people a year or more even if they prepare effectively the entire time.
You'll likely get a clearer sense of how long it will take once you start preparing.
The key to achieving your score goal will be preparing effectively, and what works best is to work on the GMAT one topic at a time, mastering each topic in turn and basically driving your score up point by point.
To see how someone who started at 250 and ended up at 780 prepared, you could read
Dalal's debrief.
To learn more about how to prepare for the GMAT in general, see this post on
How to Score a 700+ on the GMAT — A Mini Guide for Success.