[JayP]

After playing a bunch the past few days, I've realized City States are pretty awesome. The thing is that you have to almost go all-in and milk them for all their effectiveness or it's tough for them to provide any benefit.

In my current game, I went for a heavy gold production route and used it to pay off the City States for influence. Once they become allies, cultured City States give out 12 culture/turn. That's huge in the early game. And once you start getting enough culture to adopt the policies specifically for City States look out. If you get the one that slows your degrading of influence and the one that adds Science from every friendly city state you're pretty set. After that point and getting every City State I can afford to be allies with, nearly half of my culture and science per turn was being generated from the city states (along with huge food surplus from the maritime ones).

EDIT: Forgot to mention that using City States is a great way to get additional resources (both strategic and luxury). I found myself never lacking for iron or horse (which I in turn flipped the iron/horses in my territory to other Civs) and selling excess luxury resources to other Civs goes a long way in paying for City State's influence.