Cultural victory is best to achieve with many puppets and only one or two cities of your own. Some guy at CFC had already beaten 1700 AD and is going for something around 1560AD.
http://forums.civfanatics.com/showth...385143&page=19 The more puppets you have, the more money they bring in when all their tiles have trading posts. With 15-20 puppets, you can easily get 300 gold per turn without golden age.
The only way to get puppets is to allow the AI to settle and then capture his cities. The more and faster they settle, the better you are. Neighbor AIs which are very close though should be eliminated rapidly.