I made it through my first victory today on a small map. I mostly stuck to building factories, if close to my shipyards, and research buildings otherwise. I built a few markets, but didn't see much benefit. Most of the time, I kept my slider at 50/50 manufacturing/research, so the economic buildings didn't seem to do anything. I started going into the negative at the end of the game, unless I pulled the slider a bit towards the economic side, but the game was in the cleanup phase by then. I also didn't find myself building any farms. Is there are rule of thumb as to when these buildings are beneficial?