Were they all Jewish? The Gentiles (Greek) contributed many members to the early Church.
Right, many Gentiles were saved as well. All of the gospels were written either by an apostle (Jewish) or an understudy (Jewish); Paul wrote about a dozen of the books, and he takes great pains to describe his Jewish background; John the Jewish, Beloved disciple (apostle) of course wrote the 3 John Letters and Revelation. The author of Hebrews is not known with certainty, but the title of that book alone argues strongly for a Jewish author - it could have been Paul or maybe Apollos.
"Were they all Jewish? The Gentiles (Greek) contributed many members to the early Church."
The disciples were commanded to preach the Gospel, "first to the Jew, then the Gentile." Many of the first converts, even in Greek cities, were Jewish. There were many Hellenized or Romanized Jews, like Paul, who was a Roman citizen. Of course, many Gentiles did come into the fold very early, even during the lifetime of Jesus.