I prefer to have an equal number of males and females. If your talking back ups your going to want an extra male and an extra female because you never know which fish is going to not want to spawn.
Remember when looking for your pairs that the female is just as important (some may say more) than the male is. Many fish favor the female's side more than the male's side. It can be hard to look past a flashy male but ALWAYS ask for pictures of the female so you can look at her structure and branching. This is really important if your looking to produce good halfmoons.
If you have any more questions don't hesitate to ask.. there are plenty of people here that use a variety of different methods so you'll get a bit of every opinion... which IMO is much better than just getting one opinion from one website.
BTW.. have you considered joining the IBC? (The International Betta Congress). There is a WEALTH of knowledge available to new members not to mention the experience of breeders who have been breeding bettas for decades and breeders producing show quality fish. You can also join the 'Betta Pals' program and qualify for a free pair of fish.