I find an interesting way to succeed as the Greeks is to not stretch yourself thin trying to combine your provinces too early. Wait and build up your troops in each of your cities. This is much more difficult to defeat for the computer as they will have huge armies in a few cities instead of many cities with only a few troops per. Start by building up Sparta and advance on Macedon through Corinth, Athens, Larissa etc... Thermon may be tough to hold onto because it is kind of blowing in the wind. Build up a large amount of phalanx units to bolster all of those skirmishers. If you can use the Skirmishers as a "hit and run" tactic on the enemy as they appoach - every bit helps.