City Spamming, I call it rapid expansion. When it comes to either way you word it, DON'T . .. .. .. . with the Romans. They get that early republic, which lets you rush a settler when you have 4 pop so you can still have a city with 3 pop and get a settler out, then with good movements and attacks against barbarian villages and getting to friendly villages (YOU MUST BE FAST) you can get that free settler (100 gold), so there's two cities. Then if you've settled your other city already with the rushed settler, you prolly have 3-5 pop if you settled it in a good spot, then you make a new settler and settle it.
In other words, the Romans are prime for rapid expansion.
However, you don't NEED to do this, but I prefer it since I'm not that good at getting less than 5 cities to produce a lot of gold or science =/ I need the cities so I can get more science and gold faster.
And also, Cookies>Romans>Tacos>Japanese>Mongols>Arabs>British