The 3rd map has the Zaibatsu, the Russians, an the Hare Krishna. Respect Gangs tend to hate each other, so, when you go into a gang member s are and start killing them left and right, you tend to make them mad, but at the same time, gain a lot of respect from another gang. Respect is good, because once you gain a lot of respect from one group, you can then receive missions which they will then give you money for. Keeping an even balance between all gains will keep your respect each gang has for you to around neutral, allowing you to complete missions for all gangs. There are many weapons to choose from, and are good for close-up killing, long range, blowing up cars, and many other purposes.
Guns are usually hard to come by.
Also, on each map, there are 2 or 3 junkyard sites. The easiest way to make money is to perform missions for a certain gang, after they respect you. Just follow the arrows, and they will guide you to telephones. Try to find the Elvis clans. They consist of 7 or 8 guys all dressed the same, walking in a single file line.