My final setup in my first Rome campaign had Italia as my main recruiting province. I had the training field in Roma (these are provincial capital only), plus the Colosseum, Pantheon, and a level 4 library. The barracks was in Ariminium, auxiliary barracks was in Neapolis, and level 3 armorer was also in Ariminium. I think the rest was only enough temples to maintain neutral public order and the rest food, with a permanent "Bread and games" edict going. It was my most valuable province, earning nearly 5000 per turn.