The Gospel According to St. Paul

Paul had never met Jesus in person. Unlike the Twelve, he had never been among the disciples since Jesus began his earthly ministry. According to the criteria set forth to find somebody to replace Judas, Paul definitely failed to qualify to be one of the Twelve. The criteria were:
Wherefore of these men which have companied with us all the time that the Lord Jesus went in and out among us,
Beginning from the baptism of John, unto that same day that he was taken up from us, must one be ordained to be a witness with us of his resurrection. (Acts 1:21-22)
Yet, Jesus appeared to Paul on his way to Damascus (Acts 9:4-5) as well as in some other occasions (Acts 18:9). There is no doubt about his apostleship. However, since he did not spend the three years of earthly ministry with Jesus, we don't expect Paul to have witnessed and experienced the miracles, healings, exorcisms, conflicts with the Jewish authority, the Sermon on the Mount, the triumphant entry into Jerusalem, the Last Supper, Crucifixion and Ascension etc. These are components of the gospels preached by the other Evangelists.
In the epistle to the Galatians, Paul explained more how he went to see Peter and obtained his understanding and approval. There was no contradictions in the gospel preached by both of them. Therefore, they were able to divide their labour: Paul and Barnabas preached to the Gentiles while Peter, James and John to the circumcised (Galatians 1:18-2:10). So, what sort of gospel was Paul preaching to the Gentiles? The gospel must be different from that of Peter and yet does not contradict Peter's as well as being appropriate for the Gentiles. That is to say, there should not be too many unnecessary Jewish materials.

In his own words, Paul wrote
For I am not ashamed of the gospel of Christ: for it is the power of God unto salvation to every one that believeth; to the Jew first, and also to the Greek.
For therein is the righteousness of God revealed from faith to faith (Romans 1:16-17)

First of all, Paul is not ashamed of the gospel of Christ.
One wonders why people would feel ashamed to believe in the gospel of Christ. I suppose it was because Christ had died a shameful death in the eyes of his contemporaries. Christ was crucified. Therefore, in the eyes of his contemporaries, Christ was a failure or even worse, a criminal. The preaching of Christianity cannot leave out the crucifixion part of the Jesus event. Nowadays, the crucifixion of Jesus is no longer a taboo topic. It is difficult for us to imagine the kind of embarrassment Christians had to face when they told people that they believed in a crucified Jewish carpenter. Nowadays, believing in a crucified Jesus is easier and more comfortable.

What is the gospel of Christ according to Paul?
It is the power of God for the salvation of everyone that believes. In this gospel, the righteousness of God is revealed.
It is rather abstract and theological. I guess it means God is almighty. God uses His power to save us. We need to believe in Him if we want that salvation. God shows His righteousness when He saves us.
Still, such an exposition is not satisfactory.
Of course God is almighty. He could use His power to do anything. But why does He bother to use His power to save us? The standard answer is that God saves us because He loves us. I am not sure whether Paul buys this idea.
The next question would be why believing in God would obtain salvation. OK. This is the famous "Justification by Faith" theology of Paul. I am sure we will come across his exposition in this epistle.

Dear Lord, in Your love we trust. Amen.