The Apostles proclaimed the good news of Jesus Christ. The message they taught has five essential points:
You Have Already Been Forgiven
 Forgiven: The sins of all people throughout history were forgiven and forgotten on the Cross of Christ. Only one single sin, the eternal sin of unbelief, was not forgiven. Forgiveness is no longer the issue; unbelief and a sinful inner nature are the two remaining issues in salvation.
How You are Saved
 Saved through Faith: All are forgiven but not all are saved. Only when that last sin of unbelief is turned to faith in Jesus Christ does God remove your old sinful nature and replace it with a new heart.
 Born from Above: With a new heart you become, for the first time, a "clean vessel"; the Holy Spirit now has a place within you to live. It is God's indwelling life that saves you.
Your Life with Christ
 Union with Christ: With the Spirit of Jesus Christ (as His Holy Spirit) living in you, His presence makes you literally righteous in your born again heart because Jesus, the Righteous One, is inseparably joined as one to you; you cannot sin in your new spirit because Jesus in you cannot sin (1 John 3:9). And, you possess eternal life because Jesus is Eternal Life. With God's life now living in you, Christ becomes your power to do the works of God and to live a righteous life. Jesus lived this very same life of faith by the power of the Holy Spirit that He received at His baptism.
 Living by Faith: Your redeemed spirit still "lives" inside the same mortal "house" that you had before you were saved. Your physical body has not yet been redeemed; it awaits a future redemption (Romans 8:23b). Unlike your redeemed and righteous inner spirit, your mortal body is still dead because of sin (Romans 8:10). This is why believers can still sin. More importantly, it is the reason why you live by faith. In your own human strength, you cannot live righteously; but, as you follow in faith the indwelling life of Jesus Christ, He will live out His righteous life in you and do His good works through you.
Note: The "Holy Spirit living in you" and "Jesus living in you" mean the same thing; see Romans 8:9-10. Also, "heart," "spirit" and "nature" all mean the same thing. Your inner spirit is the real you while your human body is your temporary "house" (2 Corinthians 4:16, 5:2).
What has Happened to the Gospel Since the Apostles
The Christianity that you are experiencing today is actually two opposing systems of belief integrated into one religion. The predominant element is the now obsolete and discontinued system that was based on human performance; the lesser part is the true Biblical system of faith based on the finished work of Jesus Christ.
Early in the Christian era, the Gentile believers began separating from the Jewish believers. As a result, the Gentiles began interpreting the Bible without a proper understanding of its Jewish context. Lost was the fact that God had completely ended the Old Covenant Law and replaced it with New Covenant grace. These two distinct and opposite covenants (human works vs. Christ's works) were combined into a hybrid religion that is nearly universal in Christianity. This mixed religion is not from God because it contradicts the teachings of Scripture. At issue is this: is your standing with God going to be based on your own righteousness or on Christ's righteousness? God does not offer a blending of the two (Galatians 3:12); you either rely on yourself or you put your trust in Jesus Christ.
Being saved never involves human works nor does it involve guilt and shame. Good works and righteous living come after you have the power of Jesus Christ living in your born again heart. The true Biblical Gospel is perfect in its simplicity: your sins were forgiven and forgotten on the Cross of Christ; in addition, God will give a new heart filled with His own righteous life to all who believe. Bible Verses Explaining the Gospel of Jesus Christ