Ground slam Zerk Up damage

Hello everyone, I just got my Echoes of creation. I don't see how to increase my damage much now.

https://pobb.in/kUuTPZHoX-1P

https://poe.ninja/builds/settlers/character/Nesales/Gstraghaar?type=exp&i=4&search=class%3DBerserker%26name%3Dgst

I know the weapon isn't perfect.

But before paying 10divines for a weapon xD , I wanted to get your advice on how to increase my damage and get your advice. Thanks :)