Best way to build gerome

He's comparable to his own mother(Cherche) but without the access to IVS.

either go for the Brave axe BA/Desperation build:
Weapon:Brave axe+
Special:Luna/Draconic aura
A:Deathblow
B:Desperation
C;Flexible
Seal:Brash assault

Or Just go with his default weapon and focus on him on being a cavalry killer.

tbh just go to Cherche's hero page and pretend u got a neutral one and you're gucci

Actually, opposed to what they have said here. I built up my own Gerome.
Premature build.

He can tank Ayra with a bit of setup (IE fortify Fliers), so it works wonders

Close Def 3 on A and S Seal, QR3, Bonfire, Slaying Axe+def
This is overall a really good flying tank build if you need one. If you don't want this, then go full cherche.