Overall, Gotham has some similarities to the comics, but it also makes significant changes to characters and plotlines to make it more unique for the TV series. For example, some characters' personalities and backstories are altered.
In most cases, Gotham is canon to comics. It incorporates many elements and storylines from the comic universe, maintaining consistency and respecting the source material. However, there might be some creative interpretations or minor deviations for the sake of the TV show's narrative.
Gotham fiction often features a dark and gritty urban setting, like the city of Gotham in Batman stories. It usually has complex characters, both heroes and villains, with deep backstories. There's a sense of mystery and danger lurking in every corner of the city.
It's inappropriate. Fanfiction should be a creative way to expand on the story, characters and concepts of the original work in a positive and respectful way. 'Gotham sex fanfiction' goes against this by introducing sexual content which has no place in the Gotham narrative and can potentially damage the reputation of the Gotham franchise.