[Shovah32]

Place alot of temples, sure they cost 400 gold and are easily destroyed but they give a great boost (and every 5 increases your max dominion by 1). As for preaching, i put the majority of my priests on my borders to hold enemy dominion at bay but i still spread some around my empire so dominion dosnt go down there either.

And yes, priests can affect neighbouring provinces (or else only stealth priests could remove enemy dominion)