Well, they basically rule over the other gangs of the district they're in with an iron fist. Anyone who crosses them is targeted and put on their to-clobber list. While they aren't known for murder (rather, they let their "prey" live as an example to others), they can be pretty brutal and grusome, especially the leader Thatch. They have about 30 members, divided into groups of 3 or 4 at a time, and scattered among their district.
As for Rico's gang, there's only about six of them (Rico included); Don, the leader, Rico, who earns the gang money from street or club tournaments/events, Marie, the scout who gathers intel, Max, the mechanic who maintains and fixes the other members' bikes (Rico doesn't have one), Roxie, a classy gal with connections, and Lazarus, the brains. As for a name for them, I haven't come up with one. Care to lend a hand?