==That's why you go to war and free the oppressed land that just happens to have those strategic resources and luxories that you need!==
War before Chivalry or better yet Military Tradition, and without strategic resources already aquired, is such a slow and messy business. I like to concentrate on peaceful empirebuilding and scientific advancement until Sipahi come online, at which time everyone dies. Because of my late onset warmongering, it's important to peacefully grab as much good land as possible.
Of course, switching to Monarchy early has the advantage of reducing the number of turns in Anarchy, which I'm told partially depend on the size of your empire, but if you a. don't start crazy citybuilding until you have Monarchy and b. are unable to build settlers during the turns of Anarchy, you could lose out on the best land.