If Christians would spend more time being a Christian instead of defining to other Christians what a Christian is, we would have less arguments such as this one. My simple answer is given by Peter in Acts 2:
Acts 2:38-39 Peter said to them, "Repent, and each of you be baptized in the name of Jesus Christ for the forgiveness of your sins; and you will receive the gift of the Holy Spirit. For the promise is for you and your children and for all who are far off, as many as the Lord our God will call to Himself."
But this is just the "beginning" for the Christian. We have the rest of our eternal lives to grow in the grace, knowledge and love of the ONE who has saved us, redeemed us, and called us to Himself.
Blessings
Edited by John 10:10, : added "knowledge"