Not going to laugh, was just curious. The AI in FF is more based around providing a challenge at high difficulties (immortal, deity), than around providing a challenge at lower difficulties (noble and below). Personally, I wouldn't suggest playing at anything less then noble, simply because the AI is rather abysmal at the lower levels. However, this is being worked on, and the difficulty is gradually increasing. Note, because FF isn't releasing anything soon (they are working on a MAJOR overhaul of the entire system), the AI isn't being improved for it.
The other reason for asking though is that what you are doing right now, while perfectly OK for settler, isn't going to work quite as well as you increase the difficulty. Generally, one of the best things to do is expand as fast as you can. At the lower levels, having just one city isn't that much of a problem. As the difficulty increases, it becomes exponentially more difficult with fewer cities. Basically, what I would recommend you doing is to expand faster, earlier, either by warfare of by settling (which one you do is dependent upon how crowded your map is, but generally settling is easier). Other than that, have fun and experiment. Each of the civs plays very differently, so what works for one might not work so well for another.
-Colin