I don't believe asking about the minimum with regards to salvation is the proper approach.
John 6:44
No man can come to me, except the Father which hath sent me draw him: and I will raise him up at the last day.
It is God who draws us to Himself. We can do nothing to approach God on our own. And when God draws us, He knows just how to fully redeem us. Leave the details and timing up to Him.