We are a kingdom of priests in the new covenant that was established. Why do you reject it? Revelation 1:5-6
As far as some OT verses showing that Gentiles will also be the people of God:
Joel 2:28 And it shall come to pass afterward that I will pour out my spirit upon all flesh...
Joel 2:32 And it shall come to pass that whosoever shall call on the name of YHWH shall be delivered ...
Malachi 1:11 ...my name shall be great among the Gentiles; and in every place incense shall be offered unto my name, and a pure offering: for my name shall be great among the heathen, saith YHWH of hosts.
Daniel 7:13-14 that all people, nations, and languages should serve him: his dominion is an everlasting dominion, which shall not pass away, and his kingdom shall not be destroyed.
Isaiah 2:2 And it shall come to pass in the last days, the mountain of YHWH's house shall be established... and all nations shall flow unto it.
Psalms 86:9 All nations whom thou hast made shall come and worship before thee, O YHWH; and shall glorify thy name.
Isaiah 56:6-7 ...for my house shall be called a house of prayer for all people.
Isaiah 49:6 ...I will also give thee for a light to the Gentiles, that thou mayest be my salvation unto the end of the earth.
Isaiah 42:6 ...for a light of the Gentiles
Isaiah 45:22 Look unto me and be ye saved, all the ends of the earth...