I started as Werner von Habsburg in 1066, got my Duchy, went somewhat pious route - choosing traits giving piety. I started to look around for easy conquests and I noticed, that when asking for a claim from the pope:
Base reluctance: -50
Barely a Duchess: +20
Woman: +50
Child: +25
(going by memory, for child and duchess, could have been the other way round)
Therefore as long as the Pope even remotely likes you, for ~300 Piety you can have almost any Ducal Claim, while for ~150 Piety any county claim, as long as the target is a child or a woman.
My ruler died quite quickly so I got his son, Otto, to rule since he was 15 for ~55 years. Here is the effect:
For 300 gold you can get 100 piety for donating to a holy order, so you can get that piety going quickly.
This is inside HRE, it's still there (alt click on HRE, realm view)
Base reluctance: -50
Barely a Duchess: +20
Woman: +50
Child: +25
(going by memory, for child and duchess, could have been the other way round)
Therefore as long as the Pope even remotely likes you, for ~300 Piety you can have almost any Ducal Claim, while for ~150 Piety any county claim, as long as the target is a child or a woman.
My ruler died quite quickly so I got his son, Otto, to rule since he was 15 for ~55 years. Here is the effect:
For 300 gold you can get 100 piety for donating to a holy order, so you can get that piety going quickly.
This is inside HRE, it's still there (alt click on HRE, realm view)