There's plenty of gangs out there, but my advice just find someone in game, help them a bit and you'll find that you stick together.
I now play with four other guys which I met all in game, some by complete accident and one because he dived in my car and said "so where we goin" and that was the first day I had ever played, a couple new and a couple old.
But trust me it won't take long before you find yourself with some guys,