Born a few days before the destruction of Planet Vegeta. Goku's parents sent him to Earth inside an incubation champer to protect him. Landing close to Mount Paozu, he was rescued and kept safe by an older man called Gohan. At first, Goku showed the violent and aggressive traits of every Saiyan. Still, after an almost fatal fall in a ravine that sent him into a coma, he became much calmer and had even lost the memories he had of his homeworld.
Grampa Gohan, as Goku would call him, began to train the young child in martial arts. Gohan would discover that Goku was forced to transform at the sight of a full moon. As such, he instructed him never to do so. Unfortunately, one day Goku would transform into a giant ape and unknowingly kill Grampa Gohan in his rampaging. After recovering from the event, Goku had lost his memories of Gohan and concluded he was abandoned by his parent and left to survive in the wilderness of the mountain, which he did.
While surviving on his own, he would meet Bulma, who was looking to gather all seven Dragon Balls to request Shenron a wish. As it turns out, Goku had the fourth ball in his position and joined her quest. On their travels, they would come to meet Master Roshi, Oolong, and Yamcha. It led them to gather all the Dragon Balls at Pilaf Castle after being captured by the gang controlling it. The Rabbit Mob, the leader of which gets their wish interrupted by Oolong at the last moment thanks to a well-timed Kamehameda from Goku.
With the Dragon Balls scatter throughout the world once again, Goku went back to Roshi to train with him and Krillin before the World Martial Arts Tournament. Goku was greatly challenged through the tournament but eventually came second to Jackie Chun, Master Roshi in disguise. After the event, Roshi tells Goku that he needs to travel the world to continue his training.
Goku also decides to travel the world to find the fourth Dragon Ball. While doing so, he would fight off a paramilitary group that exerted a great amount of control over the world. The Red Ribbon Army and its generals and captains attempted to defeat him numerous times as he made his way through the ranks of the groups looking for his Ball. In this time, he would come across Chi-Chi, his future wife and mother of his son Gohan.
As he defeated the various members and liberated towns, Goku was helped by locals, one of which Bora was killed by the Red Ribbon Army, leaving Upa, his son, orphan and distraught. Even though Goku had recovered the fourth Ball, he was devasted to see the pain Upa had gone through and decided to end the Red Ribbon Army for good. Then recover all the balls and wish for Bora to be alive on behalf of Upa.
After reviving Bora, Goku sets out to keep training before the next World Martial Arts Tournament. Once again, he makes it all the way to the final round but eventually loses after an incredible fight against Tien. While going back to his locker, Goku finds Krillin dead by the hand of one of King's Piccolo's sons. After chasing them, he is quickly defeated due to the exhaustion of the tournament and falls into the wilderness to be rescued by a sword-wielding master.
Goku would spend time training with the said master before confronting King Piccolo and his sons again. This time winning and killing the King before he could control the world. However, King Piccolo was able to birth one more son before his death, eventually becoming the new Piccolo. Once an adult, Goku and Piccolo would come to blows at a World Martial Arts Tournament, finally achieving his first tournament win.
Although Goku is the series's protagonist, he certainly is not the best character in DBFZ. Oh, but that is not to say he is weak. His solid pressure and space control give him many good tools to stagger opponents and have a dominating tempo. He is one of the best characters for raw damage output, and a handful of great win securing moves puts him well into the upper levels of the competition. But holding him back are his lows and high, which makes mixups a rarety for him alongside needed a team built around his potential instead of being a solid character from the outset.