Okay, I'll elaborate a bit more.
The Angel Cartel is to some extent a space mafia. Raiders are an occult group. Guristas are a sort of an ex-military third-army of criminals. Serpentis are the high-end luxury drug dealer trope. Thukkers are Thukkers.
But there isn't really a 'gang' faction nor can I recall any RPers ever trying to create one. By gang I mean containing the features commonly associated with street gangs in real life: somewhat amorphous structure and organization, consisting of linked cells, a prescient subcultural moral code, the EVE equivalent of fairly low-tech (which obviously is relative, this is EVE after all), often stemming from and thriving off of poverty-induced environments, etc. Guristas are the closest to me to the gang 'feel,' but their extreme hi-tech and militarism move them away from it. So if you take Maras in real life and scale down the size of operation and organization (they are getting to be more of a cartel than gang, these days).