There is a difference between Salvation and Christianity. Salvation is an instantaneous event when sinners believe and accept that Jesus Christ is the Son of God, acknowledge that they are sinners--i.e., have violated God's laws, can do nothing to save themselves--REPENT of their sins and believe on the Lord Jesus Christ.
There are many scriptures that address this process, e.g., "For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life." John 3:16
When the eunuch was seeking knowledge of the scriptures and encountered Philip and desired to baptized, Philip told him that if he believed "with all of thine heart, thou mayest [be baptized]. And he answered and said, I believe that Jesus Christ is the Son of God." Acts 8:37. There is a difference between lip service and belief in the heart. To believe in the heart is to be absolutely persuaded that Jesus Christ is the Son of God.
Christianity is often referred to and defined as a "religion." It is really more than a "religion." It is a relationship with Jesus Christ and it is a growning process. Young Christians--or new believers--need the "milk of the Word."
"As newborn babes, desire the sincere milk of the word, that ye may grow thereby." 1st Peter 2:2
"I have fed you with milk, and not with meat: for hitherto ye were not able to bear it, neither yet now are ye able." 1st Cor. 3:2.
Paul advised Timothy: "Study to shew thyself approved unto God, a workman that needeth not be ashamed, rightly dividing the word of truth." 2nd Timothy 2:15
Christ said, "Search the scriptures; for in them ye think ye have eternal life: and they are they that testify of me." John 5:39 Christ was not speaking to his disciples here, but to the Jews that sought to kill him. So, He told them to search the scriptures that testified of him. Ref. John 5:17-19.
"But grow in grace, and in the knowledge of our Lord and Savior Jesus Christ. To him be glory both now and for ever. Amen. 2nd Peter 3:18.
There is, therefore, much difference between those that claim to be Christians and those who are. "Now if any man have not the spirit of Christ, he of Christ, he is none of his." Rom. 8:9
Christ had a spirit of kindness, compassion, forgiveness, love, humbleness, meekness, etc. In truth, we don't see a lot of people that demonstrate the traits of Christ's spirit.
One thing--but certainly not the only thing--that contributed to Dr. Billy Graham's ministry being so successful was the fact that he realized very early in his ministry that the churches were full of unsaved people and didn't leave them out of his invitations whether Sunday school teachers, deacons, or others. Peter said, "make your calling and election sure:" 2nd Peter 1:10.