What are the dimensions of the tank?
SA cichlids are not like African cichlids, where people often over stock to spread aggression. With SA cichlids, if you over stock, most of the time you end up with battered and/or dead fish.
Many SA cichlids also show more aggression towards others of the same species, than they will towards other cichlid species, this is called Conspecific Aggression. There are different degrees to this aggression.
With Apistogrammas most aggression occurs over teritory. Females argueing over breeding sites, usually small caves, and males argueing over larger territories that will have many smaller female territories with in them.
Without knowing the specific dimensions of your tank, I would suggest starting out with a pair or a trio, one male & two females.
Some of the easier apistogramma species to start with are A. agassizii, A. borellii, and A. cacatuoides. Personally I like agassizii's the best, either red gold or double red morphs, however the most commonly kept apistos are cacatuoides, usually orange or red flash.
Then you could look at tank mates. I wouldn't suggest any other cichlids in your tank. But you could look at one or two schools of tetras as dithers, some dwarf or pygmy corydoas as a clean up crew and otocinclus catfish for algea control.