Build a wall around your camp. Have a small opening were only two people can come trough at the same time. At the opening, build the wall out from your camp so you get a passage. Put bowmens in the passage, and order them to stand ground.
Build towers along the wall. When anyone nears the wall, they will be killed by the bowmens and the towers. If someone break trough, off course you have a army waiting for them.

Dont have millions of villagers. If you have, your army wont be as large as it could have been, because of the population limit.
If you want to kill your enemy, wait until you can build Phalanxes or Hoplites. They are hard to kill and hits as hell.

If a enemy builds thousand of priests, attack him with Chariot Archers and Chariots. They are harder to conversait, and have double attack strength on priests.