Well, in many fanfictions, a common theme is their exploration of their Saiyan heritage. They could be on a quest to find out more about their Saiyan ancestors. Also, friendship is a big theme. They might make new friends during their adventures who help them see things from different perspectives, and this could lead to some really interesting character development for both Gohan and Baby Goten.
I'm not sure about who the absolute best is, but there are some authors who are quite well - known. Some of them are those who have been writing in the Dragon Ball fanfiction community for a long time. They have a deep understanding of the characters like Gohan and Baby Goten.
One common theme is growth. Since Goten is a young character, many fanfictions focus on him growing in power and maturity. For example, he might learn new techniques and become more responsible.
It's also because the Dragon Ball Z universe is so vast. There are countless possibilities for fanfiction writers to create unique storylines involving Gohan and Goten. For example, they can be sent on adventures in different parts of the universe, or they can interact with characters that we didn't see much of in the original series. This allows for a lot of creativity and keeps fans interested.
Some popular themes in Goku and Goten fanfiction could be their training adventures. They might face new and powerful enemies together and have to develop new techniques to defeat them. Another theme could be family bonding. Since they are father - son, there could be stories exploring how Goku passes on his Saiyan heritage and values to Goten.
Another fanfic could be 'Growing Up Together'. It would likely depict their childhood memories, like the times they played together, and then show how their relationship evolves as they grow older. It might also touch on how they deal with the expectations placed on them as Saiyans.
In the long run, they might realize that they need to change their behavior. They could start thinking about how to make it up to Chichi. Maybe they'll go and do some nice things for her, like getting her some flowers or cleaning the house really well without being asked. This would show that they've learned their lesson and are trying to be better sons.
One idea could be that Gohan is teaching a self - defense class and Goten pretends to be a beginner to surprise everyone. Another is that Gohan's class is a seminar on Saiyan history and Goten adds some new perspectives from his own experiences.
The plot could also focus on their relationship. Since they are brothers but from different timelines in a way. They could bond over family stories that Goten has heard but Gohan can now give a different perspective on, like stories about their father. And they might train together to become even stronger for the future battles that Gohan foresees.
Well, in such a fanfiction, it might be that Gohan's class is about martial arts. Goten shows up, and they end up having a friendly sparring session during the class. This could be a great opportunity to show how Goten has grown in his skills and how Gohan has developed as a teacher. Maybe the other students in the class would be in awe of Goten's natural talent.
One popular theme is the exploration of Gohan's dark side in relation to Videl. For example, stories might focus on how Videl tries to bring Gohan back from his dark state. Another theme could be their relationship evolving in the face of Gohan's inner turmoil. Some fanfictions also play with the idea of them teaming up against new threats while Gohan is in his dark form.