I wonder if part of the problem is actually your difficulty level. This actually works better at higher difficulties. One of the things they aren't telling you is how they are all selling EVERYTHING to the AI as soon as they possibly can. That doesn't really get you all that much at Prince or King, but at higher difficulties, it is an integral part of almost any strategy. The AI generates a lot of gold on the highest difficulties, and the player can use that to their advantage to really boost their progress.