Yes, as I have said to you, the OT timetable was always national Israel must accept Jesus as their Messiah first, before the other nations could be reached. (Zechariah 8:3-23)
Paul was no longer preaching the gospel of the kingdom by the time he wrote Romans, the gospel of Christ he was referring to there was the gospel of grace that the ascended Christ revealed to him in Galatians 1.
The biblical record attests to the following that contradict's your statement:
1. There is only one gospel as seen in Peter introducing it to both the Jews and Gentiles. He also participated in the conversion of the Samaritans. (Acts chapters 2, 8, 10) Afterward, Paul took on the mantle regarding ministering to the Gentile nations.
Also, see Hebrews 4:1-2, “Let us therefore fear, lest, a promise being left us of entering into his rest, any of you should seem to come short of it. For
unto us was the gospel preached,
as well as unto them (Jews): but the word preached did not profit them, not being mixed with faith in them that heard it.”
Jews as well as Gentiles are required to believe the good news and act in obedience to God's instruction to acquire what God has promised.
2. All of Paul's letters were directed to born again believers in churches he had previously established. The epistles focus primarily on what is acceptable conduct for those born again children of God.
3. Reference to Water baptism and Infilling of Holy Ghost in Paul's Epistles:
Paul instructs the born again Corinthians concerning the relevance of their water baptism in the name of Jesus:
Is Christ divided? was Paul crucified for you? or were ye baptized in the name of Paul? 1 Cor 1:13
He goes on to say:
I thank God that
I baptized none of you, but
Crispus and Gaius;
Lest any should say that I had baptized in mine own name.
And
I baptized also the household of Stephanas: besides, I know not whether I baptized any other. 1 Cor 1:14-16
Those whom Paul mentioned water baptizing:
And
Crispus, the chief ruler of the synagogue, believed on the Lord with all his house; and many of the Corinthians hearing believed, and were baptized. Acts 18:5
The elder unto the wellbeloved
Gaius, whom I love in the truth.
Beloved, I wish above all things that thou mayest prosper and be in health, even as thy soul prospereth.
For I rejoiced greatly, when the brethren came and testified of the truth that is in thee, even as
thou walkest in the truth. 3 John 1-3
I beseech you, brethren, (ye know the
house of Stephanas, that it is the firstfruits of Achaia, and that they have addicted (devoted) themselves to the ministry of the saints,)1 Cor 16:15
Paul’s epistle references pertaining to Spirit and water baptism associated with salvation:
(Rom 6:3-5, 1 Cor 1:15-16, 1 Cor 12:13, Gal 3:27, Eph 4:4-5, Col 2:12, Titus 3:5-6, Heb 4:1-2)