We get to the end of the first missionary journey. Before retuning to Antioch the team returned to the cities they had visited, to encourage the disciples.
Including Lystra where it had all gone horribly belly-up. If you are like me then you do your best NOT to go back to Lystra in case you get worshipped as a god or stoned all over again. You had to be full of grace and godly courage to go back there. I take it to mean that even though the previous account didn't give any indication of conversions there, that there had been some. God had been at work in the situation that was, humanly speaking, horrible. 14:21 is a call to see unpleasant situations in which we think there is no fruit through God's eyes, not ours.
In each city they strengthened disciples and encouraged them to stay true to the faith. Notice the content of this strengthening encouragement:
1. Their message for disciples young in the faith was "we must go through many hardships to enter the Kingdom of God (v22). Get into the right mode of thinking right from the start. Do we teach new believers right from the start of their Christian life that this is a struggle against opposition that hates Christ and will hate us? Jesus told the disciples "remember when the world hates you that it hated me first. It hated me without cause." With integrity we ought to warn people that being a disciple isn't a cakewalk.
2. They appointed elders in each church, to provide for future teaching. Note that they committed them to the Lord with prayer and fasting, just as they themselves had been commissioned by the Antioch church. I take it that this means that the Holy Spirit was setting aside these people for leadership, and the way of discerning and seeking the Spirit for guidance about leadership was prayer and fasting. I assume that these elders weren't teachers only therefore, but that they too were called to be leaders for the extension of the Kingdom.
In v26 there is a great sense of closure. They returned to where they had been committed to God's grace for the work that was now completed. Their summary of their work: the door of faith has been opened to the Gentiles. God's grace has gone somewhere completely unexpected. He blew wide open the expectations about how he must work and who he wants in his family. They gathered the church and told them everything. That must have been a good meeting, full of joy. I bet even the other prophets and teachers who had been involved in hearing the Holy Spirit speak at the start realised that their expectations had been too small. God had done immeasurably more than they could have imagined.