Question: ckii how to gain piety?
Answer: Invite and appoint a lord spiritual with high learning skill: ... 
Granting a temple to a courtier gives piety (25 piety if barony tier, 50 piety if county capital)
Tutor two children. ... 
Some personality traits award Piety per month. ... 
Theology Focus can give 100 piety in seclusion event.
Warfare: