How do I get the best sanitation/available building slots

[wealthmonger]

With a faction other then the Sassanids. I'm thinking of taking one of the Celts and switching religions for more sanitation. Which one should I switch to? and at the same time I'm looking for which one gives me the most open building slots, least amount of slots needed to counteract any negatives from that religion.

More to the point on the individual province level. If I make a rank 5 Celt general governor of a province, I'll get +6 sanitation in each region and +6 public order from his skill tree. If I build a religious building that gives sanitation in that province, what should the rest of the buildings be in the province to make it a big money maker? What religion/building? would any resource be good for this scenario?