JUST AS A WARNING... there might be a few spoilers within!
MAFIA
Leader - Salvatore Leone
Car - Mafia Sentinel
Clothes - tuxedos, can have sunglasses
Weapons - Handgun or a Shotgun
Territory - Saint Mark's in Portland
This is the first gang you'll work for. They have a lot of control over Portland, but several rival gangs have recently begun to attack them and attempt to take more control of the area. They run the Red Light District too. They are dangerous when you anger them in the game. After they hate you, steer clear of Saint Mark's unless you have to. Shotguns blow up cars FAST.
DIABLOS
Leader - El Burro
Car - Diablo Stallion
Clothes - Denim, red and blue bandanas, jeans
Weapons - Baseball Bat, Handgun
Territory - Hepburn Heights in Portland
These guys are small time. Their cars are really cool though, with those flames on the side. Most of their business involves the production of adult literature. Even after they dislike you, it's still no big deal to travel through their territory because all they have is bats. Occasionally one will pull a pistol though, but hardly at all.
TRIADS
Leader - ??? unknown... sorry. None is specified in the game that I know of. Car - Triad Fish Truck
Clothes - blue suits
Weapons - Baseball Bat, Handgun
Territory - Chinatown in Portland
They will be your biggest enemy in Portland. They just as harmless as the Diablos. Their vans aren't much of a big deal either. It's funny to walk through Chinatown and hear the stupid phrases they scream-
"Somebody call a medic!"
"I see pain in your future!"
"And the winner by knockout is..."
"Easy, dragon-breath!"
COLUMBIAN CARTEL
Leaders - Catalina, Miguel
Car - Cartel Cruiser
Clothes - Hawaiian shirts, jeans, leather boots, hats with crocidile teeth on them
Weapons - Uzi, AK47
Territory - Fort Staunton in Staunton Island, Cedar Grove in Shoreside Vale
These guys are your main enemy throughout the game. Nearly every gang in Liberty City hates them, except the Yardies. They produce a drug called SPANK, which is their main cash flow. Catalina, their leader, is the woman who shot you in the chest at the start of the game. You used to work for them until Catalina shot you.
Their weapons are formidable, and their Cruisers sound cool, though a pain to drive at some points. Most missions that involve them will usually be stopping SPANK distribution and sales.
YAKUZA
Leaders - Asuka, Kenji
Car - Yakuza Stinger
Clothes - Business suits
Weapons - Handgun, Uzi
Territory - Torrington, in Staunton
These people will be the first gang you'll work for in Staunton Island, and you'll work for them for most of the rest of the game. Their cars are awesome. The Yakuza Stinger is really fast, yet still can absorb a good amount of damage. Their main source of income is Kenji's Casino. They hate the Cartel, and most of their missions involve stopping their drug operations. They also have a lot of crooked cops under their payroll in the police department so the cops will ignore them.
YARDIES
Leader - King Courtney
Car - Yardie Lobo
Clothes - tan pants and vest, black shirt, black hat.
Weapons - Baseball bat, Handgun
Territory - Newport in Staunton
You'll work for these guys somewhat in the game. They're just about the only gang in Liberty City that's openly on the side of the Cartel. Their business is selling the Cartel's SPANK for them. They're small time and aren't any big deal really.
The car is pretty cool, because you can mess with the hydraulics on them.
RED JACKS
Leader - D-Ice
Car - Hoods Rumpo XL
Clothes - black baseball cap and pants, red shirt
Weapons - Handgun, Uzi
Territory - Wichita Gardens in Shoreside Vale
They are small time like all the other optional gangs, but I like working for these guys. Most of the vans in this game suck royally, but their vans are actually REALLY cool. The Hoods Rumpo XL drives real fast and is real tough.
They don't seem to have any kind of special business that supports them other than stealing valuables. They wish to get rid of the Purple Nines, who are moving in on their territory.
PURPLE NINES
Leader - ???
Car - Hoods Rumpo XL
Clothes - black baseball cap and pants, purple shirt
Weapons - Handgun, Uzi
Territory - Wichita Gardens
These guys are the smallest gang in Liberty City. They are almost exactly like the Red Jacks in every way except for their purple shirts. They drive the same vehicles, they wear similar clothes, they just steal to support themselves, etc. The Red Jacks want these guys gone because they are invading their territory. After you complete the final mission for the Red Jacks, these guys will vanish completely.
