African cichlids usually refers to rift lake cichlids and more specifically mbuna. Not always but that's usually what people mean when they say african cichlids.
WIth that in mind, a great stock list for a 55 gallon is
yellow labs (Labidochromis Caeruleus)
Ps Acei ( Pseudotropheus Acei)
Rusties(Iodotropheus sprengerae)
With 5 of each aiming for 1 male per 4 females. These species aren't too picky about the gender ratios though. They are colorful and some of the more peaceful mbuna.
Another good option for mbuna is a lab/demasoni tank.
15 Pseudotropheus demasoni with 6-7 yellow labs. It's a stunning tank full of color and activity.