The Wedding at Cana.
Changing water into wine may not seem like the greatest way to start Jesus’ ministry, but as miracles go, it was a generous, quiet act which kept a wedding from becoming a disgrace. And it is an act on par with the feeding of the multitudes. It marks Jesus ministry as life giving - Moses turned water to blood as a curse, a plague, but Jesus made the water into the best wine, a blessing. And his disciples, in on the secret, put their faith in hiim.
Clearing the temple
John already doesn’t seem as concerned to put things in the same timeline as the other Gospels. He orders events,at least partly, by their significance. The clearing of the Temple introduces the theme of Jesus' death and resurrection: “Destroy this temple and I will raise it again in three days.” John has jumped ahead in the story to give us a glimpse of the climax of Jesus ministry, his crucifixion for our sins. This segment also ends by pointing to the disciples response to this prophecy - they believed when the prophecy was fulfilled at the resurrection.
Jesus, on the other hand does not put his trust in people. He knows that the crowds, so amazed at his miracles, have not yet come to any steadfast faith.