Well, one key event is Goku's early battles against various foes. He faces off against enemies like Raditz. Another important part is his training and growth in power during this part of the story.
A plot could revolve around a time - traveling character who goes back to the time of the Tenkaichi tournaments in Dragon Ball Z. This character could accidentally change some events, leading to a whole new set of battles and power - up scenarios. Maybe Goku doesn't get the senzu beans he needs at a crucial moment, forcing the other fighters to step up more.
Vegeta is also highly popular. His pride and his journey from villain to anti - hero are rich areas for fanfiction. Writers can delve into his internal struggles, like his constant need to prove himself stronger than Goku while also dealing with his new - found family on Earth.
Well, it depends on how you define fanfiction. Technically, Dragon Ball Super is an official continuation of the Dragon Ball series. However, it does have elements that feel like fanfiction. For example, some of the power - levels and new forms introduced seem a bit outlandish and more like what a passionate fan might come up with rather than a strictly logical progression from the original story. But it's still an official part of the franchise so it's a bit of a gray area.