If we did not have to contribute anything ourselves, we all would be saved no matter what we do. But that is not what the gospel teaches.
Which gospel?
And the thief on the cross did exactly what after he put his faith in Christ?
If we have to add anything to the death of Christ, then the death of Christ wasn't good enough. If the death of Christ isn't enough to satisfy God's wrath against sin, how can our righteous deeds, which are as filthy rags in His sight?
When one adds anything to Christ's death, that's the thing that one says confers salvation. It's saying that Christ's death isn't good enough and whatever one adds is what one is putting their trust in for salvation.
It appears that you completely misunderstand the Sacrifice on the Cross as well as the Gospel of the Grace of God...
Jesus died on the Cross because there is nothing we could do to provide the sacrifice necessary for Salvation...He paid our price; all of it...Jesus became sin, for us...Jesus gave us His righteousness, because we couldn't produce or provide any ourselves...We are incapable...
Jesus gave this free gift to the Gentiles, the pagans to make His people Israel jealous...