Well, first off, you should read Monster: The Autobiography of an LA Gang Member by Sanyika Shakur as it goes further in depth into the life in a gang than we ever could on this blog, including initiation, expectations, and perspective about life in a gang. It’s going to be uncomfortable to go through, but each member of your group should read it and discuss it together.
Most gang members are not professionally trained fighters (except in the cases when they are and with use of military service becoming a method to get a leg up on the competition as they join of their own accord, that number is growing, former convicts as cops is unlikely due to extensive background checks, former convicts or former and current gang members as military personnel does happen). They come in under the header of street fighter, so most of what we talk about on this blog isn’t really applicable. However, our street fighting tag may be helpful to bring it into perspective. I really suggest looking at the video of the thug versus the MMA fighter for a good example of the differences.
The thing about gang members is that they don’t really know how to fight, but doesn’t mean that they’re not dangerous. Gangs recruit their members young, often as young as ten or eleven. They usually do so from single parent families or kids whose parents spend most of their time working in order to support the family, but this can leave the child unsupervised and feeling neglected. The gang is insidious because it becomes a surrogate family for the child, with older members shaping how the child sees and responds to the world. This sense of brotherhood a gang provides is the strongest lure and any child the gang has access to can be at risk, this includes kids from wealthy families who the gang members may now access to through flourishing social media.
Gangs have been a part of American society from the beginning. Gangs always arise out of ethnic minorities groups that are given limited opportunities for societal advancement. When presented without the option to make money or provide through traditional routes, individuals will turn to crime. The oldest historical gangs in the U.S. were the Irish, then came the Italians (it should be noted that Italian Gangs and the Mafia are two separate things), etc. Gangs are not the same as Organized Crime, though they can move in that direction. They are still criminal enterprises. You should figure out what kind of gang it is that your characters belong to as the structure of a national gang may be different from a local gang. It should be remembered that the qualities needed to create a gang are not specific to any racial group or any more likely, gangs are part of the human condition and rely on sociological factors to form and function, not innate traits.
As for combat: knives and guns will be preferable to bare hands (though they’ll use those too). Brass knuckles, tire irons, crowbars, all may be part of the gang bangers arsenal.
Baggy pants are useful because they can hide the outline of a knife or gun tucked into the back. A hood may limit peripheral vision, but it also makes one appear more threatening. Baggy clothes widen the frame of the body and in the dark (sometimes even daylight), a person can seem larger, more imposing. This can be useful if they are looking to shake someone down or are trying to protect their turf. It’s important to not just think about what’s appropriate in a wide sense, but think about what will make sense from the perspective of the characters in the story. What do they know? What are they trying to accomplish? Why do they dress this way?
Once you get a beat on why they behave the way they do and what their goals are, the methods they’ll use to fight will start to make sense. A gang member is most likely to be influenced by two things:
1) What he learns from getting the crap beat out of him (which isn’t much).
2) What he sees on television.
Your gang member may be part of a local gym, in which case, if he practices any form of fighting at all, then it’ll be something that will provide some possible form of social advancement (traditionally boxing, MMA, etc).
I hope that helps.