The Faction effects all tie into one another. Understanding how they relate is important to surviving early game.

With the 50% increased penalties to public order on account of being psychotic bible obessed nutbags, the 3 extra priests passive is critical to success. This lets you mass convert single provinces by staking them all in one place. Or spread them out to help collect more funds threw taxes and increased public order, to make up for the lost treasury bonus. Thanks to the resistance to death from natural causes you should be able to field several long lived sages that will be essential to controlling the plebs, buffing/disrupting armies, and best of all reliably CONVERT other agents/armies. You can now be true to Roman style, and just pay their friends to stab them in the back. (*^‿^*) The 0 resistance to occupying Roman territory allows you to quickly cannibalize the heathens in the west with little problems as it turns out Romans dont like living knee deep in their own dung surrounded by full stacks of German/Hun Hordes. Early expansion into thier lands after you stablize is advised, but pick ur opening move against them carefully. This also allows for easy recaps after any rebellions (if thier roman rebels), making 50% increased penalties to public order for foriegn religion less opressive. Heveanly Cities lets armies heal faster after a cap to deal with any upcoming rebellions or counter attacks. Which is pretty much every time as you will be at war with everyone and every culture is going to hate you more then gamers hates the letters DLC in a row.