I'm uploading this game mostly because a friend of mine told me how weak he thought Gaia was versus a rush. To be fair, the usual 2TC 6:00 classical buildup probably would have lost this game for me. But it is a common misconception that that is the only viable Gaia buildup. Here I pull off a 1TC 5:10 classical (I've done it as quick as 4:30 before, but food was tighter on the start for this scenario) and instantly put up two counter barracks. A little bit of micro allowed me to push him back. After that, I raided to much effectiveness. Later on, he went heroic while I went 3TC boom. When I found his wood and gold villagers near the end though, he gave up.
The buildup I used for this game, or any game where I'm Gaia vs. Rush (i.e. Loki, Kronos, Oranos, etc.) is the following:
Villager 1: Guild (Hunting Dogs) -> Huntable food
V3: Gaia forest (when going against Thor and Odin be careful where you put it because of Forest Fire)
V4: Manor -> Gold
V6: Temple -> Gold
When V7 is done training, you should have enough food to go classical. Hit the button, and move one of your food villagers to wood. Then get the pickaxe upgrade at the guild while you're going classic. Build a manor or two around your towers.
The classical age god isn't all that important. I like to use Leto because of the Spider Lair GP, but Oceanus can be just as good. Its really a personal preference thing. If I were going against a Greek, I'd pick Oceanus.
When you hit classic, you should have enough wood to not only get the tower upgrade, but also be able to put up two counter barracks. Do that. At counter barracks, train a turma or two and then put cheiroballistas on autoqueue. Make the turmas heroes and then fight off the rush.
Realize this: in almost any rush situation, the enemy will be using some form of infantry. This usually means Hersirs, Hoplites, or Oracles. Mixed in with those are some myth units. If you micro properly, this can be a very easy fight. Make sure you don't neglect your economy at the same time, though, since the game will continue even after the initial rush.