No offense man, but i think you have to start lower. You know, there is a lot of complain here about the AI beeing too easy... so, just consider yourself at the funniest side of the river....
i mean, you will have (with default setup) a lot more playability than most of us, because AI still beats you. So, enjoy beeing beaten by AI. I mean it.
I suggest you start at easy level and try some "stabilization" strategies early on (build up good defenses, at least one "mobilized" army (hanging around, outside cities, to counterattack any attempt).
After beating at easy, it will be funnier at the highest level. In a month or so, you will be asking again how to improve the AI. In the meanwhile, please...
ENJOY!
C-ya