First, use the Law to bring the knowledge of sin to make sure they are really converted.
Then the parable of the sower.
Finally, Romans chapters 6-8.
Romans 6-8 deals with every major aspect of the salvation experience (the cross, justification, Law vs Grace, walking in the Spirit, repentance, water baptism, and Holy Ghost baptism. Plus they'll be getting a lesson on how to systematically study scripture.)