This is one of the first Wildcards in the game, available quite early. However, unless you're playing as Greece, it may only be used after you develop Political Philosophy and get the respective slot in your Government. It is a nice way to get one of the early Great Generals, even without building an Encampment. This could turn to be really useful for a militaristic civilization, bent on early conquest, or it may be a pure waste of effort - it all depends on your current strategy, and the neighbors you got. Sometimes you won't even need a General to conquer them, other times you simply won't make it without one. So, you should think carefully whether you really need a Great General so early - if you don't, then there's no reason to use Strategos.