The Feast of the Epiphany
This Sunday, the second reading will be from Ephesians 3: 2-3a, 5-6. The link includes the intervening verses. Be sure to read the other readings for context.
I suspect that the vast, vast majority of the current Christian population is gentile in its origins.
Early in the Church’s history, it experienced growth at an incredible rate - on the order of thousands of people being baptized in a single day. I don’t think any of us are likely to witness conversion on such a drastic scale in our lifetimes.