@TipsyTentacle When I played Civ 5 it pretty much always went like this:
I would focus on something like science or culture or just making citizens happy, but eventually someone would try to invade me, so I'd switch all of my cities to production, make an ungodly number of ships and military units, steamroll whoever just tried to invade, and then just go back to chilling and trying to make their citizens happy too.