Power and dominance are common themes. Since Goku Black was already a powerful character, in the female versions, the focus often remains on her strength and how she uses it to get what she wants.
Another theme is identity. As a female version of Goku Black, the fanfics often explore how she is different from the male counterpart in terms of her personality and how she views herself within the Dragon Ball world. It's an interesting exploration of character identity.
Many female Goku Black fanfictions revolve around the theme of redemption. Given that Goku Black was originally a villain, the female counterpart may also start off on the wrong foot. Writers like to explore her journey towards redemption, changing her ways and perhaps even becoming a hero. Additionally, themes of friendship and rivalry are common. She might form new friendships or rivalries with other characters in the Dragon Ball world, which adds depth to the story.
One common theme is power struggles. Since Black Goku is a very powerful character, when he crosses over, there are often battles to determine who is the strongest in the new combined universe.
A common theme is power and corruption. Since both characters are power - hungry in different ways, many fanfictions explore how their thirst for power corrupts them further. For example, they might go on a rampage across different universes to gain more power.
Love and redemption can also be common themes. Sometimes the harem members help Goku Black to find a new path or redeem himself through their love. It adds an interesting layer to his character.
The theme of love against all odds is also quite prevalent. Given their different origins and the fact that Goku is already married in the original story, their relationship in fanfics has to overcome many obstacles. This could be social, moral or even physical (like dealing with other powerful characters who oppose their union), but they still find a way to be together, which makes for an interesting read.
One common theme is growth. Both caulifla and goku are Saiyans, so fanfics often focus on their growth in power, like learning new techniques.
Friendship and mentorship are also common. Goku is often seen as a mentor figure to Caulifla in these fanfics. They form a bond through training and fighting side by side. Another theme could be the exploration of different universes. Given that they are from different universes in the Dragon Ball series, fanfics may play around with the idea of them exploring each other's worlds and cultures.
Power and training. Since Goku is known for his power - seeking, his brother in fanfics often has a similar drive. They might train in unique ways or discover new forms of power.
One common theme is empowerment. Since Goku is already a very powerful character, in these fanfics where she's female, it often emphasizes her strength even more, showing that gender doesn't limit her abilities.
One common theme is the power - dynamic. It often shows how a female character interacts with Goku's extreme power. For example, she might be in awe of it at first and then strive to reach a similar level.