Matthew was written to the Jews showing that He was the long awaited Messiah. The miracles show the power of the Messiah. Nine times Jesus was called the Son of David, connecting Him to the kingly line of the Jews.
Mark was written to the everyday Roman showing Jesus as the Son of God. Not only did he write to show Jesus as the Son of God but also the Servant of God. Mark records more miracles than any of the other of the gospel writers.
Luke wrote in Greek a through account and from the view of being a physician, showing that not only was Jesus the Son of God, He was also the Son of Man. He wrote showing that Jesus was Champion of the poor and oppressed.
John wrote his gospel to the world, showing the deity of Jesus. There are seven "I am" claims that Jesus made. Look them up and see what they are.
2. 8:12; 9:5