The message of the Gospel has never changed.
We need to simply follow Jesus’ Great Commission.
Later He appeared to the eleven as they sat at the table; and He rebuked their unbelief and hardness of heart, because they did not believe those who had seen Him after He had risen. 15 And He said to them, “Go into all the world and preach the gospel to every creature. 16 He who believes and is baptized will be saved; but he who does not believe will be condemned. 20 And they went out and preached everywhere, the Lord working with them and confirming the word through the accompanying signs. Mark 16:14-16, 20
The main thing is to keep the main thing the main thing.
Satan constantly wants to divert us from the main thing.
I marvel that you are turning away so soon from Him who called you in the grace of Christ, to a different gospel, 7 which is not another; but there are some who trouble you and want to pervert the gospel of Christ. 8 But even if we, or an angel from heaven, preach any other gospel to you than what we have preached to you, let him be accursed. 9 As we have said before, so now I say again, if anyone preaches any other gospel to you than what you have received, let him be accursed. 10 For do I now persuade men, or God? Or do I seek to please men? For if I still pleased men, I would not be a bondservant of Christ. Gal. 1:6-10
The Simple Gospel is:
…I declare to you the gospel which I preached to you, which also you received and in which you stand, 2 by which also you are saved, if you hold fast that word which I preached to you—unless you believed in vain. 3 For I delivered to you first of all that which I also received: that Christ died for our sins according to the Scriptures, 4 and that He was buried, and that He rose again the third day… 1 Cor. 15:1-4
Peter’s first message told people how to receive Christ.
36 “Therefore let all the house of Israel know assuredly that God has made this Jesus, whom you crucified, both Lord and Christ.” 37 Now when they heard this, they were cut to the heart, and said to Peter and the rest of the apostles, “Men and brethren, what shall we do?” 38 Then Peter said to them, “Repent, and let every one of you be baptized in the name of Jesus Christ for the remission of sins; and you shall receive the gift of the Holy Spirit. 39 For the promise is to you and to your children, and to all who are afar off, as many as the Lord our God will call.” 40 And with many other words he testified and exhorted them, saying, “Be saved from this perverse generation.” 41 Then those who gladly received his word were baptized; and that day about three thousand souls were added to them. Acts 2:36-41
After salvation, we continue in fellowship with other Christians.
42 And they continued steadfastly in the apostles’ doctrine and fellowship, in the breaking of bread, and in prayers. 46 So continuing daily with one accord in the temple, and breaking bread from house to house, they ate their food with gladness and simplicity of heart, 47 praising God and having favor with all the people. And the Lord added to the church daily those who were being saved. Acts 2:42, 46-47