I find that there are a rather long period from when you meet AIs and start trading and get engineering almost right away. Then it takes a long time to tech to steel/rifling. And during this period I almost never tech economics myself and it's not always you get a good trade. And then it's the anarchy required to get into free market. Getting economics isn't really needed until you have constitution (which you are in no rush for if you have the pyramids) and are ready to push toward assembly line. Thats at least how it most often turns out for me... Is something off? Here I'm in isolation with a PRO leader and have access to stone. (Building pyramids) I think that the trade routes can be very beneficial. Sort of a scenario tailored for the castles at least I can't figure out a better one!