All I can say is after having tried a couple of starts with Gauls: Do not try to rush your neighbor using the Gaesetae. I repeat: DO NOT try to rush your neighbor using the Gaesetae. They will die just an archer looks at them. It's borderline ridiculous, you pump a lot of resources into them, and two archers will leave them completely helpless. From what I can say, anybody who thought this was going to be a good civ for early domination was thoroughly mistaken.