The audience of the Gospels was centered on the lost sheep of the house of Israel and the preaching of the Kingdom was the message.
Jesus came first for the lost sheep of Israel. They are the Jews who already belonged to God by faith. Jesus was going to make a new covenant based on faith; the old covenant was based on the purification works of the law and not based on faith.
When Jesus came, God cut off all the Jews who did not already belong to Him by faith, and God hardened those Jews so while Jesus walked the earth, the cut off Jews could not get saved yet. See, God bound those faithless Jews over to the same place as the disobedient Gentiles.
All the Jews who already belonged to God by faith, they now had to go through Jesus to remain God's. Jesus said he would not lose one that God gave him.
John 12:32 And I, when I am lifted up from the earth, will draw all people to myself."
Jesus also said that when he is crucified, then all people could come to him to be saved.
Romans 1:16 For I am not ashamed of the gospel, because it is the power of God that brings salvation to everyone who believes:
first to the Jew, then to the Gentile.
Romans 2:9 There will be trouble and distress for every human being who does evil:
first for the Jew, then for the Gentile;
Acts 3:26
When God raised up His servant, He sent Him first to you to bless you by turning each of you from your wicked ways."
Acts 13:46 Then Paul and Barnabas answered them boldly:
"We had to speak the word of God to you first. Since you reject it and do not consider yourselves worthy of eternal life,
we now turn to the Gentiles.
Acts 18:6 But when they opposed and insulted him, he shook out his garments and told them, "Your blood be on your own heads!
I am innocent of it. From now on I will go to the Gentiles."