Other than building materials and slaves, the prestige of your citizens houses is also vital, certain building or constructions in the vicinity of a house may cause it to become so prestigious that it reaches the next level. Occupants of such prestigious house are also more productive creating more goods for your burgeoning ecomony which can be used by other buildings or traded, either for goods which are in tight supply or gold. You'll definitely have to keep a good balance of most types of goods in order achieve your goals.