Start with quality breeders. With some patience the best approach is to grow some juvies out from a quality source. Buying adults in a good ratio can work, but costs more and is more likely to have aggression problems initially.
So many times people buy the cheapest fish(i.e. mixed african tank) they see and then end up with either a bloodbath or fry that no one has any idea what they are. Another common pitfall is even with good stock is one of this, one of that which can again lead to aggression and hybridization issues.
What tank size are you looking to use? You should have at least a 40 breeder. A 75 or 125 will give you a lot more options, in terms of choice and number of species.