Why don't you try finishing up the tutorial? You might've mastered the first step, but nailing down the fundamentals is what's important.

Qualify from a round without falling over even once

Qualify from your first round

Equip your first cosmetic item

Beat the Womb/Utero without taking damage

Unlock ending A.

Complete all the arena’s challenges.

Defeat His Holiness Escribar.

Achieve maximum health.

Bring all offerings to the Lord of the Salty Shores.

Get the 9 original sword hearts.

Achieve maximum fervor.

Save all Kissers of Wounds.