I just completed a victorious campaign as Germany (disappointingly done via space race). But the major gripe with my performance was that my treasury was hundreds in debt and regardless of heavy emphasis on building economic buildings, going full into Commerce policies on a island dominated map, having many cities (x2 more than closest rival), all my cities having trade route to my capital, limiting military buildings to lower building upkeep, and throughout most of the game (Marathon setting) I had the smallest army, even until the end. I've split tile improvements for balanced mining / trade posts / farming, or even maxing out trade posts. Despite all this, I was almost always in debt. I even try to specialize cities for specific purposes (economic, research, production types). But all that does is heavily limit me from a bunch of higher end buildings, especially the ones that require you to build so many of a specific building as a prerequisite. A bit different from past Civ games where if you have a sprawling, well developed civ with great populations abound, I found myself being very rich. But that's not working out in Civ 5. What am I doing wrong and what can I do to get even decent money flow?