The DBZ Saga spans three years time. Unfortunately, the information that I have is limited, since only a small fraction of the episodes have been translated into english yet. But there is still a sufficient amount here. All charachter names and Important phrases in the passages are in Italics.
YEAR 1: starts by dealing with the mystery of Goku's origin. A powerful invader from space arrives. His name is Raditz, and he claims to be Goku's brother. Both he and Goku, he says, are Saiyans, incredibly powerful warriors from the planet Vegeta. Goku was originally sent to Earth as a baby to conquer it, but a memory erasing head injury prevented this. Now Raditz expects Goku to finish the job, or else. Goku teams up with his greatest enemy, the demonic Piccolo to battle Raditz. In the end, Goku sacrifices his own life to defeat Raditz. But passing on, Raditz reveals that two other Saiyans, far more powerful than him, are on their way to Earth.
The rest of the first year of DBZ is spent searching for the DragonBalls with which to bring Goku back to life so that he can face the two new Saiyans, Goku's quest to train under the godly King Kai, Piccolo's harsh training of Gohan, and the eventual battle with the two Saiyans, Nappa and Vegeta. Vegeta will become Goku's nemesis throughout the series. Goku defeats the two Saiyans after killing most of Goku's friends. Yamcha, Chaio Zu, Tienshinhan, and even Piccolo are killed at the hands of Nappa. Unfortunately, with Piccolo gone, the Earth God Kami-sama has also gone with him, and Earth's DragonBalls. Because of this, none of Goku's friends can be wished back to life.
YEAR 2: A quest begins to Piccolo's home planet Namek in an effort to obtain another set of DragonBalls with which to wish Piccolo and the other allies back. Goku is too injured to go, but Gohan, Goku's best friend Krillin and the intrepid if difficult Bulma agree. The journey is long and fraught with dangers, but eventually they make it to Namek, only to find that the vile Emperor Frieza is already on Namek. Frieza is a kind of "poor little rich monster", whose hobby is destroying planets, is also after the DragonBalls, hoping to wish for immortality.
Goku, nearly healed, learns of Frieza and sets off for Namek in a special spacecraft that lets him train in up to 100 times Earth's normal gravity (100Gs). King Kai warns Goku that Frieza is too powerful for anyone to beat, and angering him may endanger the universe itself, but Goku is determined to help his friends. Vegeta, however, has also healed and is also headed for Namek with a lust for the DragonBalls and hatred for Goku in his black heart.
YEAR 3: is a non-stop battle between the minions of Frieza, the ever more powerful Vegeta, and the now equally powerful Goku. Nost of Namek is destroyed in the epic fight, and Goku finally transforms into a Super-Saiyan, a super-powered version of himself with blond hair, green eyes, and a blazing energy aura.
