How do Gentiles fit into God's plans for Israel?

What is God's plan for the relationship of Jewish and Gentile believers in Yeshua (Jesus) in the body of Messiah? And how does this relate to Jacob's prophecy of the "fullness of the nations" (m'lo ha-goyim) and the tribe of Ephraim? How did the early apostles understand this prophecy? A message shared at Beth Ariel, a Messianic synagogue in the Los Angeles area.