I played as Greece on Prince following a strategy article on apolyton. Held off all social policy purchases until I bee-lined to the Medieval age, and then completed the Patronage tree before building my 2nd city. I was able to build both Stonehenge and the Great Library by turn 56 (article says to have them both by turn 50) so I did OK. After that, I was able to become allies with every single CS I met, with a maximum of 500 gold per CS (some were "bought" with only 250). You really see everything: food, research, culture, resources, even Great People etc get significantly pumped up, so that you're almost living off the teat of City States - which allows you much more freedom in what you want to do.
In my war against the Egyptians, Belgrade provided the entirety of my siege (4 cats) and some other units. I rolled Egypt, and in the process let Belgrade get conquered so that I could Liberate them, and now they love me sooo much. Plus, it was really cool when I declared on Egypt - in the same turn about 6 CS's also declared on Egypt, 3 of which were on their borders. Right now, at about 300 AD, I control the northern half of my continent, I've got about a 15 unit army consisting of one Great General, those 4 cats, and the rest a mixture of Longswordsmen and Knights positioned along my southern border watching those untrustworthy Arabs.
It's a neat strategy. For point of reference, after getting the Patronage tree completed, my CS relations only degraded 0.37 per turn (instead of the usual 1).