Pretty much everything is missing in between His birth and the time of the beginning of His ministry.
The gospel of Luke does make mention of one event during His adolesence:
Luke 2
42When he was twelve years old, they went up to the Feast, according to the custom. 43After the Feast was over, while his parents were returning home, the boy Jesus stayed behind in Jerusalem, but they were unaware of it. 44Thinking he was in their company, they traveled on for a day. Then they began looking for him among their relatives and friends. 45When they did not find him, they went back to Jerusalem to look for him. 46After three days they found him in the temple courts, sitting among the teachers, listening to them and asking them questions. 47Everyone who heard him was amazed at his understanding and his answers. 48When his parents saw him, they were astonished. His mother said to him, "Son, why have you treated us like this? Your father and I have been anxiously searching for you."
49"Why were you searching for me?" he asked. "Didn't you know I had to be in my Father's house?" 50But they did not understand what he was saying to them.
51Then he went down to Nazareth with them and was obedient to them. But his mother treasured all these things in her heart. 52And Jesus grew in wisdom and stature, and in favor with God and men.
Now interestingly, verse 52 is the last verse of Luke chapter 2, and beginning with chapter 3, Luke skips any and all events in the life of Yahshua up until the time that John the Baptizer was preparing the way immediately preceeding Yahshua's public ministry.
The important question that you ask - why is there, for the most part, no record of the events in Yahshua's life that took place during His formative, adolecsent, and young adult years? After all, most certainly the things that took place in His life would have all contributed to making Him the man that He was at the time of His ministry. Many Christians insist that "if it's not in the bible, then God didn't consider it important enough for us to concern ourselves with." Such a narrow minded viewpoint, however, is completely the OPPOSITE of Truth.
The scriptures instruct us to "walk as Christ walked." But how are we supposed to do this without knowing what He did in order to reach the elevated level of righteousness that He reached; that is, the level in which the Eternal God could say to Him "You have become my Son. With you I am well pleased." These are the words that were spoken of Yahshua at the time John babtized Him, which did not happen until Yahshua had lived the majority of His shortened life.
Again, that would be like telling a young child to become a great professional football player without giving him any instruction on how to play the game during his growing years.
So again, why are these important years skipped altogether in the bible? Is it because God doesn't want us to know about the life events of Yahshua that led Him to become the man He was as an adult? Or is it because He wants us to seek out the answers?
There are works out there that propose ideas of Yahshua's life journeys and experiences that led up to the beginning of His ministry, the Aquarian Gospel of Jesus the Christ being one of them.