There is a trick some call the Barb Factory where you leave the Barb city alone, station a Dip or Spy in a fort outside the walls and bribe everything that gets produced by the city. If it is far enough away from your own cities they will all be NONE-support. I have even heard of people sending a Settler and a Dip to a tiny island far from home with no defender in hopes that the Settler creates a city, the undefended city gets taken by Barbs, and the Dip harvests the Barb units produced by the city. That way the city is working for you, but not affecting your grand city restlessness numbers or suffering massive corruption and waste. Pretty neat.