When I first began playing this game my biggest problem was being in the negative financially so I began learning what buildings and improvements helped me with wealth and hammers. So I been trying to get all buildings in all cities. I am now rethinking this strategy as I think it is the reason that I'm not enjoying as much combat early on unless someone declares war on me. Am I on the right track with this thinking?
Yup, you don't need most of them. My rule is that I avoid building health and happiness buildings until I nearly need them (not until I actually need them, otherwise there is a productivity loss--at that point, start whipping them). For example, don't be building aqueducts at city size 3 when your health cap is somewhere around 10. It's just a waste of time.