Setup a Gang
You can create your own gang in-game by using the command /gcreate. You can then invite players to your group using the /ginvite command.
You can send messages within your gang by using '!' specifier followed by the message (Eg. !Hello). The gang talk can only be seen by the gang members and nobody else.
Leaving a Gang
You can leave from a current gang by using /gleave command. However, the gang leaders cannot leave their gang, but close them using /gclose.
Use /gcmds to list all the available gang commands.
Use /gstats to see the statistics of your gang.
If you have more questions feel free to use /ask