If you want to be safe from credential stuffing, you need to make sure that every single password is absolutely unique and unguessable.
And theres only one way to do that.. use a password manager. If you want an extra layer of protection, also use unique usernames and email addresses. Many email providers accept a plus and some arbitrary characters between the username and @ sign. If not then something like https://guerrillamail.com can help you be unique.