The first century Church didn't really teach Universalism as a distinct subject, although I can find it in the writings of the first disciples of the Apostles to indicate that it was a passing point of doctrine that was acknowledged and perhaps understood to a limited extent. The first century Church had the biggest part of their message devoted to proving the crucifixion and resurrection of the God-man, Christ Jesus, His Lordship "over all," repentance, a day of judgment coming, proving one's repentance by one's deeds, love, the absolute necessity of fellowship with fellow believers, holiness and warnings against false doctrines coming from docetism, gnosticism, etc.
Their message was essentially/primarily God having proven the Lordship of Jesus Christ by raising Him from the dead, and thereby obligating all to repentance and belief in Christ Jesus. Basically a modified version of the 4 spiritual laws pamphlets put out by Campus Crusade For Christ:
1. God has a wonderful play for your life;
2. Jesus was raised from the dead by God;
3. Through faith in Jesus you're justified from all things that you weren't justified by through the law of Moses;
4. Repent, make restitution, and believe the Gospel.
They were proclaiming both the ending of the polytheistic pagan culture and the monotheistic religious culture through Jesus Christ that had existed up until then. People were devoted to their rituals, to all of the African, Greek, Roman, and Asian gods. There was never this alls well that ends well abomination that many people nowadays mistake for Biblically [Cross and Blood-Centered] Christian Universalism.