YES! I've finally done it! I've beaten Regent level!
The invasion of Babylon was quite long, and I had to constantly send Immortals and later Knights by Galley to the other continent. Luckily, I conquered the Great Lighthouse from the Babylonians, so my galleys could sail past the seas between the two islands with no risk. The Babylonians had pikemen, which slowed my victory by a couple turns.
The Greeks were next. I attacked with a galley-full of Knights in the south, and swooped down with my Army and more Knights from the former Greek cities in the north. The Greeks had Pikemen and Hoplites, but all of their city defenders were Regulars. I fed them to my Veterans and Elites.

. I earned a great leader and built an army full of knights. (Can you tell I like Knights?

)
The English were further south, and were a piece of cake. They conquered Russia before I even discovered them, so the cities of Moscow and St. Petersburg were soon taken. The English cities had one pikeman and one spearman (

) each. I got another army from that war and put knights in them. In four turns I conquered England.
The game ended in 1402, soon after I built my first Cavalry unit. I am now known as "the Lion-Hearted" with a score of about 6800, a new high score for me. (my last was 812

)

Thanks so much for the advice. If I hadn't known about mining the grassland and irrigating the desert I would have never won.
