The Early Believers
Whilst we have read of Ignatius of Antioch setting up bishops and the like, there was another stream of Christianity which retained its New Testament roots. Due to its mode of operation it was somewhat like an underground organisation (kind of helpful in times of intense persecution) and yet by the year AD 300 it had pretty much taken over half the Roman empire.
There are not a lot of records about this body of Christ in the period AD 80-300, but we have enough to know it worked. Using Christ’s requirements of Matt 7:16, I will let their fruits speak for themselves.