Another one of the earliest Policy Cards, Agoge will boost your earliest military units' training rate significantly. It is very important for militarized civilizations, which rely on early conquest - they generally need to churn out a sizable army within the first 30-40 turns. However, civilizations in peril of invasion could also use the Policy effectively, and come up with an army where before there were only easy pickings for the enemy.
This Policy is a Military one, and is a very good option for a general Military Policy for the first 50-100 turns. You can occasionally replace it with Discipline (if threatened by Barbarians), with Survey (if you want to boost early reconnaissance), or with other unit production-oriented Cards as the need arises.
In Attic Greek, “agoge” meant “rearing” – the rigorous education and training mandated for all Spartan males. Besides cultivating loyalty to Sparta, the state schools included instruction in military arts, pain tolerance, hunting, dancing, singing, public speaking, and all manner of things that make for a warrior. There was also a form for Spartan girls, although the curriculum was somewhat different (intended to prepare them to give birth to warriors). The practice of agoge waned in the 3rd Century BC throughout Greece, but was revived in some places after the Roman victory in the Achaean War.