Since I could see that pottery would be really hard, I tried to keep my houses at small casa level as long as possible and rather build 4 Luxury palaces. That got me already to a prosperity of 53 when the city was still trying to become stable (few tents, shacks, hovels) and later to 61 (only 4 tents in farmland). After that (having stockpiled pottery) I added bathhouses. Sure enough the city kept devolving and evolving over the next 2-3 years but prosperity went up to 69 and finally 77. Also - as you can see - I won the battles wit 5 legions and no walls or towers.