So you can be in a gang that is enemies with your faction? That's pointless. Gangs should just be used inside the prison walls, or just replace the factions plugin.
I'm not sure how the prison looks so spare me, but for gangs instead of it bejng outside of prison make a little world inside the prison. Make it 2k by 2k or such and make gangs be able to get like 5x5 claims and in the "gang land" pvp is enabled. Also if you are not free you have to pay an entrance fee to the gang.
The prison features and add-ons are confusing me a bit. 3,000,000 for a gang? With the current economy balance setup it's a bit difficult for most players (ruling out those who no-life it). Gangs exist inside a prison as well. It's a great idea to rival other gangs inside the prison. Gangs are created both outside and inside of a prison. Plots exclusively to Free ranked players has me confused. Such a childish concept. Prison has so much potential with amazing plugins that can be found on curse and spigot. Most modern servers have these plugins. Mineverse has always been behind on plugins.