The Lord's signs through Paul throughout Acts were meant to confirm God's Word through Paul that He had turned from Israel.
That God had turned from this in Romans 15 that had been Prophesied:
8. Now I say that Jesus Christ was a minister of the circumcision for the truth of God, to confirm the promises made unto the fathers:
9. And that the Gentiles might glorify God for his mercy; as it is written, For this cause I will confess to thee among the Gentiles, and sing unto thy name.
10. And again he saith, Rejoice, ye Gentiles, with his people.
11. And again, Praise the Lord, all ye Gentiles; and laud him, all ye people.
12. And again, Esaias saith, There shall be a root of Jesse, and he that shall rise to reign over the Gentiles; in him shall the Gentiles trust.
To this in Romans 15 that had not been Prophesied:
13. Now the God of hope fill you with all joy and peace in believing, that ye may abound in hope, through the power of the Holy Ghost.
14. And I myself also am persuaded of you, my brethren, that ye also are full of goodness, filled with all knowledge, able also to admonish one another.
15. Nevertheless, brethren, I have written the more boldly unto you in some sort, as putting you in mind, because of the grace that is given to me of God,
16. That I should be the minister of Jesus Christ to the Gentiles, ministering the gospel of God, that the offering up of the Gentiles might be acceptable, being sanctified by the Holy Ghost.
17. I have therefore whereof I may glory through Jesus Christ in those things which pertain to God.
18. For I will not dare to speak of any of those things which Christ hath not wrought by me, to make the Gentiles obedient, by word and deed,
19. Through mighty signs and wonders, by the power of the Spirit of God; so that from Jerusalem, and round about unto Illyricum, I have fully preached the gospel of Christ.
Paul, as his habit was, based his ministry, on a principle found in both - that which was prophesied as to the Gentiles but did not come to pass due to Israel's failure, and that which came to pass through Paul's obedience unto his calling as to this issue: - Romans 15's:
21. But as it is written, To whom he was not spoken of, they shall see: and they that have not heard shall understand.
22. For which cause also I have been much hindered from coming to you.
And he himself was "born out of" Israel's "due time" Acts 3 calling, under the Twelve, 1 Cor. 15:8.
He was saved unto this calling among the Gentiles before Israel's prophesied, due time redemption and calling among the Gentiles, now on hold, thus Paul's "now the God of hope fill you with all joy and peace in believing," etc.