Where did Christianity first begin to spread outside of israel?

Right after the Ascension of Christ in 29 AD. The Apostles would have carried the message far and wide and start 1st century churches.

The first Christian communities outside of Jerusalem appeared in Antioch, Ephesus, Corinth, and the political center of Rome. The original church communities were founded by apostles and numerous other Christians, soldiers, merchants, and preachers in northern Africa, Asia Minor, Arabia, Greece, and other places. Over 40 churches were established by 100, many in Asia Minor.Paul was responsible for bringing the Christianity to new parts of the world such as Ephesus, Corinth, Philippi, and Thessalonica. By the end of the 1st century, Christianity had already spread to Rome and to various cities in Greece, Asia Minor and Syria. Major cities such as Rome, Ephesus, Antioch and Corinth served as foundations for the expansive spread of Christianity in the post-apostolic period. Christianity spread quickly throughout Asia Minor.