If you are new to Soulsborne games: Kill the Cleric Beast first. Technically. Beast Cleric is an easier and slower boss fight than Father Gascoigne.
Can Father Gascoigne help Cleric Beast?
You can summon Father Gascoigne to help you fight the Cleric Beast (you must have the Hunter’s Ancient Bell). It can be summoned near the fountain where you encounter the first Brick Troll in Yharnam. The benefit of summoning Father Gascoigne is that he can help you fight the enemies guarding the Great Bridge.
What is the right level to fight Father Gascoigne?
20 Recommended Level: 20 It should be noted that Hell starts with the short version of his melee weapon and then upgrades it to a longer blade to indicate the second phase of the fight.