Wonder no longer, as Peter had about 3 years with the Lord who taught him some things about grace, including that He would be made a ransom for many, as Israel rejected Him, and thus that
And that repentance and remission of sins should be preached in his name among all nations, beginning at Jerusalem. (Luke 24:47)
And Paul alone was not the recipient of special revelation, but the Lord said that He had many more things to say to them, and Peter's sermon in Acts 2 was part of that, and was the gospel of grace, of forgiveness and the Spirit by faith in the crucified and risen righteous Christ
To Paul was revealed the mystery more deeply as concerns how this theologically worked, and of the ecclesiology of the one new man.
Which in other ages was not made known unto the sons of men, as it is now revealed unto his holy apostles and prophets by the Spirit; That the Gentiles should be fellowheirs, and of the same body, and partakers of his promise in Christ by the gospel: (Ephesians 3:5-6)
But the established point remains that both Jews and Gentile converts came to God as damned+destitute sinners, who trusted in the mercy of God in Christ to save them, believing on the crucified and risen Lord Jesus to save them, and confessing Him as Lord. One gospel of salvation by grace thru faith to multitude classes of peoples, but offered to Jews first on Pentecost, that a remnant would not follow the path of their leaders. To the glory of God. Amen.
Look, you can believe as you will. Obviously. But know that without rightly dividing God's word there is no stedfastness in doctrine. WHo gets water baptized? And how? When? What about tongues? and signs and wonders and miracles and faith healers and which miracle is from God and who judges that and where are WE in God's plan and timeline for man and what are our duties as believers and what is going to be our future and are we going through the tribulation, etc, etc, etc. Ad nauseum. OR you can rightly divide His word, like He has INSTRUCTED us to do, and be at peace. Not being like a child, but a mature member of the Body, ready to do His work and be an effective ambassador for Christ. It's your choice. It's your salvation. Work it out.