Hmmmm.. I agree with Fionn's sentiments (if not his arguments) we need infrastructure to support our military (even moving units on roadless terrain is a hasle) As many, many polls, discussions, chat logs and rpg threads have stated: we are, like it or not, a warmongering naiton, period.
What we need to do is build towards that, not against it. If we are destined to have a strong military, lets have the infrastructure to support it, not just the cities to support units, as Amirsan stated. Units, to be effective, need roads to rapidly move from one part of the empire to the other, they also need gold to be supported, that means we must get our techs and luxuries elsewhere, here is where trade comes in. Now, expansion for it's own sake is folly, if we plan to take every piece of jungle in hopes of aquiring rubber later on in the game then an endless war could very well be our history on this land. We already have the largest empire, let's see if those resourses fall within our borders (they most likely will) if not, we shall deal with the problem when it arrives... we are living in the future, building panzers and looking for the resourses needed for them long before their time.
If we also plan on concentrating most of the building time on military units, then we must defend our cities from foreign culture to avoid flipping. Universities, libraries, temples... all of these help our military plans by preserving the territory our armies have gained, therefor they should be, and are, inside the budget.
As I stated earlier, if we plan to warmonger, we should do it right, and not just take territory that can be easily taken back by their previous owners, or someone else.
Ehecatl Atzin