John 2:11 This beginning of miracles did Jesus in Cana of Galilee, and manifested forth his glory; and his disciples believed on him.
His first miracle was to turn the water into wine at His mother’s request. The disciples are just starting out with Him. They see and believe that He really is who He says He is when they see the miracle. He was proving that He was God. He had control over nature and the elements. This miracle is just the first mentioned by John as He goes about to make it clear that Jesus is the very Son of God.
We believe Him. Not because of the miracles but because we have seen our sin and the Holy Spirit has convinced us of our need of a Savior. We believe Him without the miracles but we still get to see miracles happen. God is so good to us.