To get an idea of how to visually represent gang culture I've been looking at a couple of films and music videos. I've never seen The Warriors but it's been recommended to me a thousand times by different people, the over the top dark counter-culture vibe is everything I'm into. The separate gangs all have their own uniform for identification and allegiance, and I think this is really interesting and important, from the trailer I saw gangs wearing orange suits or baseball uniform and all sorts of other things. The opening line of the trailer "these are the armies of the night" made me laugh because it's so over the top but the world that exists in the film is so enticing because of the fantasy of being a part of this brutal famous gangs. I think that's the kind of response I want from my work, simultaneously intimidating and attractive. This sort of culture is visible in so many other movies, This Is England for one, the entire movie is based around this supposedly threatening thuggish gang of teens that are actually welcoming and tender inside (until it all goes wrong but I dunno watch the movie). I actually used the poster below as a rough template for sketching out my characters because their poses were exactly what I wanted, they're all leaning about but still maintain a direct eye contact so theres a contrast of comfortableness and aggression.
My favourite example of this gang culture is a short film made by the band Best Coast in collaboration with Drew Barrymore. Whilst playing several songs from Best Coasts album a whole narrative following two opposing gangs and a Romeo/Juliet romance being created between them. I think it's purposefully filled with cliche and cheesiness and that's why I like it, and it definitely references The Warriors with the respective uniforms and general trashiness of the whole output.
Whilst not exactly gang culture I was also told my by tutor about The Molly Maguires, who were a real society in the 19th Century of Irish coal-workers who would commit acts of sabotage and activism in Pennsylvania in America in response to local concerns and grievances. Sometimes when they committed these acts of vandalism they would dress as women in order to remain undiscovered. Personally I find the image of a dirty Irish coal worker hilarious but it's an example of how dressing as a woman can be useful or empowering in some way. There's also a movie with Sean Connery that I should definitely watch soon.