Last game on Emperor I played Siam (+50% food and culture from city-states), built trading posts literally everywhere (except non riverside hills) and relied almost entirely on maritime city states for my food. Each city builds one important building (usually happiness or +gold%) while I use my gold to create allies and rush units/buildings when necessary. Patronage is the first line you take and it's very powerful. Allied city states provide you culture, food, science, military units, and sometimes great people. Great people are used to either bulb to the next era for better city-state benefits or golden ages. It is a strong (if overpowered), easy, and flexible economy.