My suggestion first off would be to start flying, and keep working towards ratings at your local FBO if you have three years anyways. When I started flight training, I thought for sure I was going to go to one of the flight acadamies as soon as I was done with school, which was going to be in a little less than two years. What I ended up realizing when I was done with school, I had just under 200 hours and was instrument rated. Suddenly, going to a flight academy did not make sense. So here I am now, a little less than three years after I took that first flight lesson with a little over 350 hours, a commercial single and mutiengine certificate and taking the CFI in two weeks. So a lot can change in three years, I would just take your training one step at a time, and see where you are by then instead of worrying what to prepare for the academies.