this takes a little time but once you have an good idea of the entire campaign map- you can literally monopolize a resource by placing a merchant on all or most of the spots. Example- silk is a fairly rare commodity- once you have found all the places that silk is produced- put a merchant on every silk "deposit" and welcome to the profits of global commerce- I had already played a lot so I knew before starting my most recent campaign where silk was- I chose the turks specifically for their immediate economic prowess- after around fifty turns I had enough merchants and had stragically placed them around the map- building many of them up on crappy resources to increase their likelihood of success- Then I took over the worldwide silk trade in one fell swoop- It was something to do- I prefer battle to economics but enjoy

God has low self esteem