The entrance into the new covenant Jesus introduced in Israel First isn't by genealogy.
The Covenant God made with certain individuals in Scripture is through genealogy from Adam to Abel to Seth to Lamech to Noah to Shem all the way to Abraham. This is the family line God chose in which to establish His covenant.
From Abraham God made covenant with Isaac and also Jacob and it passed to Jacob's sons and their descendants. Nothing has changed. It continued all the way to Jesus. Jesus is from the tribe of Judah. All the Promises of God fall on Israel's Messiah. He is the Alpha and Omega, the First and the Last.
The New Covenant was established through the death of a testator and that Person was Christ. And this covenant was promised to Israel through Him and only through Him, but God made no such covenant with Gentiles.
31 Behold, the days come, saith the LORD,
That I will make
a new covenant
With the house of Israel, and
with the house of Judah:
32 Not according to the covenant that I made with their fathers
In the day that I took them by the hand
To bring them out of the land of Egypt;
Which my covenant they brake,
Although
I was an husband unto them, saith the LORD:
33 But this shall be the covenant that I will make
with the house of Israel;
After those days, saith the LORD,
I will put my law in their inward parts,
And write it in their hearts;
And will be their God,
And
they shall be my people.
34 And they shall teach no more every man his neighbour, and every man his brother, saying,
Know the LORD:
For they shall all know me,
From the least of them unto the greatest of them, saith the LORD:
For I will forgive their iniquity,
And I will remember their sin no more.
Jer. 31:31–34.
The New Covenant, the New Testament is established with the people of Israel.
So why do you say it's with Jews only? Many Jews could not enter because of their unbelief.
The same will be said of Gentiles.
His last supper was with His disciples who happened to be Jews.
They didn't just 'happen' to be Jews. They were ordained in accordance with the covenant God made with the house of Israel. They were observing the Passover event of when God destroyed the firstborn of Egypt which led to the release of the Hebrews.
Israel first than all nations. That is those who receive Him and believe in His name.
Israel first and only.
God made no covenant with Gentiles.
At the Marriage Supper of the Lamb and His Bride Israel, know that Israel is there by Covenant.
Gentiles are there by invitation:
And Jesus answered and spake unto them again by parables, and said,
2
The kingdom of heaven is like unto a certain king, which made a marriage for his son,
And the Bride is Israel.
3
And sent forth his servants to call them that were bidden to the wedding: and they would not come.
4
Again, he sent forth other servants, saying, Tell them which are bidden, Behold, I have prepared my dinner: my oxen and my fatlings are killed, and all things are ready: come unto the marriage.
5
But they made light of it, and went their ways, one to his farm, another to his merchandise:
God has sent numerous prophets and messengers to Israel and they killed every one of them, even the Prophet-Messiah, Jesus Christ.
6
And the remnant took his servants, and entreated them spitefully, and slew them.
7
But when the king heard thereof, he was wroth: and he sent forth his armies, and destroyed those murderers, and burned up their city.
This happen when Gentiles destroyed the Temple and their cities in AD 70. It is around this time that the Times of the Gentiles started, and God began to bring in Gentiles while He blinded Israel and to make her jealous.
8
Then saith he to his servants, The wedding is ready, but they which were bidden were not worthy.
9
Go ye therefore into the highways, and as many as ye shall find, bid to the marriage. 10
So those servants went out into the highways, and gathered together all as many as they found, both bad and good: and the wedding was furnished with guests.
Gentiles invited to the wedding.
11
And when the king came in to see the guests, he saw there a man which had not on a wedding garment:
The [wedding] garment represents righteousness (of God.)
12
And he saith unto him, Friend, how camest thou in hither not having a wedding garment? And he was speechless.
The designation by Jesus of "friend" means a believer. There are no friends of God in "hell."
13
Then said the king to the servants, Bind him hand and foot, and take him away, and cast him into outer darkness; there shall be weeping and gnashing of teeth.
This means there is regret and remorse on the part of the person being cast out of the wedding.
14 Blessed are they that do his commandments, that they may have right to the tree of life, and may enter in through the gates into the city. 15 For without are dogs, and sorcerers, and whoremongers, and murderers, and idolaters, and whosoever loveth and maketh a lie. Rev. 22:14–15.
Remember, when the adversary is released from prison he gathers his army against the people of God and fire from heaven devours them all. This army is comprised of everyone who did not have a wedding garment and was cast outside the city in outer darkness, since inside the city the Light is God Himself.
7 And when the thousand years are expired, Satan shall be loosed out of his prison,
8 And shall go out to deceive the nations which are in the four quarters of the earth, Gog and Magog, to gather them together to battle: the number of whom is as the sand of the sea. Rev. 20:7–8.
14
For many are called, but few are chosen.
Mt 22:1–14.