If we ignore the casting out of demons, the first miracle, or 'sign, mentioned in Mark's Gospel as performed by Jesus was actually when he cured Simon's mother, and then he performed many miraculous cures and exorcisms:
Mark 1:30-34: But Simon's wife's mother lay sick of a fever, and anon they tell him of her. And he came and took her by the hand, and lifted her up; and immediately the fever left her, and she ministered unto them. And at even, when the sun did set, they brought unto him all that were diseased, and them that were possessed with devils. And all the city was gathered together at the door. And he healed many that were sick of divers diseases, and cast out many devils; and suffered not the devils to speak, because they knew him.
This, of course, was long before Jesus met Levi, but also of note is that Levi did not become one of the apostles. In Mark 2:14, it is made quite clear that Levi was the son of Alphaeus, but in Mark's list of apostles, Matthew was also clearly not a son of Alphaeus, but a second disciple called James was. Had the author of Mark thought otherwise, he could have listed Matthew with James as sons of Alphaeus, as he did with John and James, sons of Zebedee:
Mark 3:17-18: And James the son of Zebedee, and John the brother of James; and he surnamed them Boanerges, which is, The sons of thunder: And Andrew, and Philip, and Bartholomew, and Matthew, and Thomas, and James the son of Alphaeus, and Thaddaeus, and Simon the Canaanite,
The confusion arises because disciples are not meant to change their minds when called by Jesus, yet this seems to happen when Mark omits Levi in the list of the twelve apostles. Matthew's author resolves Levi's unexplained absence simply by not mentioning Levi at all, and by having Matthew as the disciple who was a tax collector, as Levi had been in Mark's Gospel, so that two thousand years of tradition have held that Levi and Matthew must be the same person.
This means we should not think of the disciples in terms of the calling of Levi, and it may be very possible for Jesus to have had an informal group of disciples before he met Levi.
Mark 3:14-18 do make it clear that Jesus had not ordained his twelve disciples until some time after the various miracles of chapter 2. This means that John 2:2-11 can probably only be harmonised with Mark by assuming that the disciples were at this stage only an informal group of followers, probably consisting of Andrew, Simon Peter, Philip, Nathanael and an unnamed disciple, all of whom are mentioned in John chapter 1.