No, the first sending wasn't "enough" to have reached Gentiles such as we who in time past were without hope (Ephesians 2:11-12 KJV). The mystery that included us was not revealed yet. We saw what Gentiles Paul was sent to during the Acts ministry (Acts 13:26 KJV, 1 Cor. 1:24 KJV). They feared God (Acts 13:26 KJV). They were allied with Israel, not aliens from Israel. And we saw what kind of Gentiles the Romans were (called a Jew Romans 2:17 KJV). By writing the Romans epistle, Paul had "fully preached the gospel of Christ" (Romans 15:19 KJV). Paul was sure that, when he would come to them (the Romans), it would be "in the fulness of the blessing of the gospel of Christ" (Romans 15:29 KJV).
second sending was to save Paul's life
do you deny that because that is what it says?
And saw him saying unto me, Make haste, and get thee quickly out of Jerusalem: for they will not receive thy testimony concerning me.
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And they gave him audience unto this word, and then lifted up their voices, and said, Away with such a fellow from the earth: for it is not fit that he should live.
Paul was making manifest a temple vision (prior vision) where the Lord told him He would send him far hence (Acts 22:17-21 KJV) and when he uttered it, for that "cause" he was made a prisoner of Jesus Christ for "you Gentiles" Ephesians 3:1-2 KJV. That was the "gave him audience unto this word" (Acts 22:22 KJV)...GENTILES was the "this word" and not just any Gentiles. Paul had already gone throughout preaching to Jews and Gentiles called Greeks. Paul was speaking of those cursed gentiles like the Ephesians to whom Paul wrote the letter (people like you and me Ephesians 2:11-12 KJV).
That he might finish his course with joy, and the ministry which he had received of the Lord Jesus, to testify the gospel of the grace of God (Acts 20:24 KJV), Paul: would fill up that which is behind of the afflictions of Christ in his flesh for His body's sake (Colossians 1:24 KJV), was made a minister of the dispensation of God committed unto him to fulfil the word of God (Colossians 1:25 KJV), even the mystery which hath been hid from ages and from generations, but now (then) made manifest to his saints(Colossians 1:26-27 KJV).
Without the second sending, the "those things" which the risen, ascended Lord mentioned (and later revealed to Paul 2 Corinthians 12:1-6) in Acts 9 (Acts 26:16 KJV) would have never been made manifest! There would have been no dispensation of God given to Paul, to fulfil the word of God; even the mystery hid from ages and from generations. There would have been no all spiritual blessings in heavenly places in Christ for you and me without the dispensation of the grace of God to you-ward, no mystery of the gospel, no fellowhship of the mystery which from the beginning of the world hath been hid in God, according to the eternal purpose which he purposed in Christ Jesus our Lord. And without it, you and me might as well have never been born because before it was made known that God had a mystery concerning us: we had NO HOPE.
I hope you study these things and those things out.