Ok what type of cichlids do you want New world or Africans haha. Also you know all about tank cycling correct?
But I would personally go New Worlds. Research these fish all of them will do fine in a 55 gallon. Look into Green Terror, Blue Acara, Jack Dempsey, Firemouth, Convict Cichlid, as far as tankmates go for them you could have maybe giant danios, picture catfish or Raphael catfish.
Food- Look into feeding either omega one Cichlid pellets or NLS Cichlid pellets. Make sure if you go new world the food has at least 35% crude protein in it. I would feed that 5 days a week then feed them frozen brine shrimp or blood worms 1 day then have a day off of feeding.