So too does the American. The priest will buy iron goods and items ahead of the town or AI competition, if you sell and watch carefully you can see the purchases (comparing to normal levels of consumption). He buys before starting construction. I think it is the same as for the merchant house for goods. But there sometimes is a "cheat factor" too, where the AI or the church will be able to build anyway even if no goods are present.
First expansion is 20k, second 40k, third 80k. Reputation boosts are weekly, with 10,000 being the minimum for the boost. I am not sure if 20k gives a bigger boost or not.
So far, other than one pitchmaker, I am just about to the end of June, all I have built is brickmakers. After I get about 45 (nine per town), and I am building them in tandem with wells and I am also funding church expansions as soon as I can afford a donation, I will begin sawmills, then grain and breweries. Looking at the contest, I can get cloth from the Med for a while, so I will build sheep farms next, and buy up hemp for later building fisheries. I am buy up the cheap hemp, meat, train oil and grain ahead of construction.