Jesus had just rebuked Thomas for refusing to believe the resurrection without seeing His crucifixion wounds (John 20:29).  The recorded miracles are only a selection of the many wonderful things Jesus did. Seeing miracles had been a familiar part of the disciples’ lives, and yet even they had difficulty in believing His words despite the overwhelming evidence of many miraculous signs (John 14:11).  

In the next verse, John summarises his Gospel account by saying that Jesus’ miracles, especially the miracle of His resurrection, were recorded so that we would believe.  So, is there a contradiction?  No!  The key to resolving this is in what John wrote - that the miracles and words were recorded in the book (Gospel) so that anybody could read and believe that Jesus is God the Son.  When they believe, they receive eternal life (John 3:16).
 
Think about it.  If people could not be saved without having physically seen Him, then very few people would be in His Kingdom!  And if believing was dependent on seeing miracles, then why were so many not included in the Gospel accounts?  But believing is not about seeing.  ‘Believing’ is to accept that what has been written about Jesus in the Bible (His character and saving work) is true; and that He will give new life to those who put their trust in Him (Romans 10:17).  That way, billions of people all over the world can receive eternal life as they respond to the message about Jesus – and they have!
 
The ministry of the church is not primarily to seek miracles, but to let people know about what Jesus did and said from the Apostles’ eye-witness accounts (2 Peter 1:16-18).  They prove that Jesus is the Saviour Messiah (the Christ) and God the Son (Acts 2:36).  Like that, they are not asked to rely on their own experiences, or on your testimony, however helpful they may be.  Instead, the people are putting their trust in Jesus, whose life and teaching has been faithfully recorded by the Apostles.  Our task is therefore not to encourage people into experiences but to explain the Gospel to them.  We are called to encourage them to believe what has been written so that they can put their trust in Jesus.  Try introducing them to www.crosscheck.org.uk; it may be a first step for some.