If you ever played FiveM, there are plenty of servers that uses this method of economy I'll try to describe.
Everytime you gain money from an illegal practice/product (selling guns, gun parts, drugs, etc) instead of money you should get DIRTY MONEY.
You'd have to do MONEY LAUNDERING with Organised Crime families, such Mafias, Yakuzas, Chinese Triads and etc (not GANGS tho).
This could increase the roleplay around, making those who are interested in those activities to interact a lot more with each other to actually make profit and, also, distinguish gangs from organisations (Organisations tend to be a lot stricter than gangs on this, working basically with laundry and weapons deals, leaving drugs to freelancers and/or gangs)
Correct me if I'm wrong or if it already exists in here, this is coming from someone new here whos not a part of a gang nor faction...it's just a concept I've seen in some other places that actually worked pretty well and look cool as hell.