Here's the gospel that saved and saves all descendants of Adam & Eve, and will save all who overcomes evil with good.
Mark 1:14-15
14 Now after that John was put in prison, Jesus came into Galilee, preaching the gospel of the kingdom of God,
15 And saying, The time is fulfilled, and the kingdom of God is at hand: repent ye, and believe the gospel.
Luke 13:3 . . . except ye repent, ye shall all likewise perish.
In the gospel that He preached, Christ commanded people to repent and believe the gospel. In the OT, God commanded people to repent (Ezek 18:30). In the NT, God commands all people everywhere to repent (Acts 17:30). Hence, all people are commanded to repent. Repent or perish.
If God commands people, He wants them to obey. If He wants people to obey, He knows they are capable of obeying. If people are capable of obeying, they can do SOMETHING. If people can do SOMETHING, they are in Christ because apart from Him, they can do NOTHING.
Therefore, people starts out in life already in Christ. How so?
Because God implemented the plan of salvation He devised before the foundation of the world right after the emergency occurred in Eden and saved Adam through Christ that same day He fell into sin, an act that cost the Father His only begotten Son - the Lamb slain from the foundation of the world. With Adam in Christ, all his descendants are born in Christ!
This saving act of God was manifested and revealed in the life, death, resurrection and heavenly ministry of our Lord & Savior Jesus Christ.
Repentance is change of mind for that which is good. Instead of doing evil, do good. IOW, overcome evil with good. Overcomers will Christ NOT blot out from the book of life and will be seated with Him in His throne as He Himself also overcame and sat down with the Father in His throne (Rev 3:5, 21). All NOT blotted out will be allowed entry to heaven (Rev 21:27); all blotted out will have their portion in the lake of fire (Rev 20:15).