The answer to that is easy. You should start your next brew now. Most beer benefits from some aging, and it is typical for new brewers to drink their batches before they hit their prime because it is the only beer to drink, and it is usually pretty good.
If you have a batch or two well conditioned, it is easier to wait for the new batch to properly condition.
As to how many sets of bottles you need, I would say two is required, three is better. I brew with moderate freqeuncy and have 7 kegs. (1 keg = 1 batch)
It also depends on your consumtion frequency. If you don't drink much, it is pretty easy to brew up three batches in a short period of time, and then brew a new batch as soon as a set of bottles are free. If you drink frequently, you are going to need a lot of bottles and should brew a lot initially to get a good stock pile.
One primary and two secondaries is a pretty good start.