to improve
barracks needs smith OR weapons trading (new building)
to build smith needs iron resource OR iron trading (new building)
to improve
stables needs horses resource OR horses trading (new building)
to build
boats needs timber resource OR timber trading (new building)
to improve
farms needs roads AND (for higher level farms) resource grain = easily done
to improve
markets needs:
lvl2-lvl trading building
lvl3-lvl2 trading building (lvl2 trading building would require 2 lvl1 trading so needs to be trading 2 resources)
lvl4-lvl2 trading building AND higher lvl farm
lvl5-lvl3 trading building (lvl3 trading building would require trading all tradeable resources) AND higher lvl farm
to improve
city needs:
market AND temple/church AND barracks
all in all planned trading buildings are:
iron trading
horses trading dogs are now horses resource
weapons trading (also adds weapon bonuses)(?) might just make it iron trading
timber trading
luxury goods trading
foods trading (?) change pigs to sheep, hides to cattle?
religious items trading (incense,marble) necessary for religious bldgs (?)
cities w/trading buildings will get +bonuses if the resource is available in the city and - bonuses if the resource is not available, alternatively will just allow trading when resource is NOT available.