-yeah, build up the most productive areas a lot. build ports where there is water. the port, coming at 750, will go a long way to repaying itself and severalfolds over. always worth it. trading posts especially, but not in inland isolated areas.
-always have at least a watchtower, or guard tower to keep out enemy assasins and spies.
-in the less productive areas, build taverns, inns, brothels, etc. to train the people behind the scenes...