One key moment was when Chichi first declared her intention to marry Goku when they were kids. Another was when Goku finally agreed to marry her. Also, every time Goku returned home safely from a battle, the warm reunion with Chichi was a significant moment in their love story.
One important moment was when they first met. Bulma was looking for the Dragon Balls and Goku had one of them. It was the start of their long - journey together. Another moment was when Goku transformed into a Super Saiyan for the first time. Bulma was there to witness this amazing power and it changed her perspective on Goku's potential even more. Also, when they fought against Frieza together, with Bulma providing crucial information and Goku doing the fighting, it showed how well they worked as a team.
Definitely include Bardock's last stand. His heroic yet doomed battle is a crucial part of the Saiyan lore. It could be written in great detail, with Bardock using his full power against Frieza's forces.
Well, Vegeta would be a likely character. He might be initially suspicious of the female Goku. Maybe he thinks she's a threat or just can't believe there's another Goku - like being. He could be there to add some comical moments as he tries to understand the situation.
In general, it's a bit of a toss-up. The strength of Manga Goku and Anime Goku can vary depending on the specific arcs and battles. Sometimes, it might seem like one is stronger in a particular situation, but that could change in another.
Another possible main character could be the villain that forces the two Gokus to meet. This villain could be a new, super - powerful threat that the two Gokus need to deal with. Their meeting becomes a crucial part of the story to defeat this powerful foe.
One of the characters who could betray Goku is Piccolo. Although they've been allies for a long time, in fanfiction, things can change. Perhaps an ancient evil force takes control of Piccolo's mind and makes him turn on Goku. Or it could be Krillin. He might be influenced by an outside force that convinces him Goku is becoming too dangerous. Also, don't forget about the Kais. If there's some sort of power imbalance or a threat they perceive from Goku, they might betray him to maintain the order of the universe in the fanfiction.