While Paul may have been the primary mover-and-shaker at this stage of the Church's development, especially considering the letters of the New Testament he wrote, it would be wrong to conclude that he was a Lone Ranger.
Besides Barnabas, Silas, Luke and Timothy, we hear of several other leaders emerging to help guide the Church in Acts 18. As Paul leaves Athens and arrives in Corinth, to whom he will soon write at least two letters, he meets a married couple - Jewish Romans - named Aquila and Priscilla who will join in the ministry of traveling evangelism. Paul stays with them as they share an occupation (tent-making). Later they travel with Paul back to Asia Minor and end up staying behind in Ephesus, another future epistle recipient, as Paul continues his travels.
Also in Acts 18, we hear about Apollos, a native of Alexandria, who also has taken up the call to go and preach Christ. After he receives a "more accurate" understanding of the Gospel from Priscilla and Aquila, he travels from Ephesus to Achaia, most likely landing in Corinth.