I haven't actually read this specific 'piccolo and gohan lemon fanfiction', but generally, in fanfictions involving these two characters, it might explore their relationship in unique ways. It could be about their friendship evolving, or perhaps their teamwork in new and unimagined scenarios within the Dragon Ball universe.
When writing a 'si oc kaioshin fanfic', think about the plot. It could be an adventure where the OC travels through different parts of the Kaioshin world. You also need to make the interactions with other characters believable. For example, if there are interactions with the Kaioshin themselves, show how the OC's presence affects them and vice versa. And don't forget to add some conflict to keep the story interesting.
One good 'si oc kaioshin fanfic' could be about the character's journey in the Kaioshin realm. For example, an OC (Original Character) might start as a novice and gradually learn the ways of the Kaioshin, facing various challenges along the way. They could encounter different species and have to use their wits and newfound powers to overcome obstacles.
One idea could be a story where Beerus and Kaioshin have to team up to face a new and powerful enemy that threatens their universe. They start off with their differences but gradually learn to work together and respect each other's powers.
One possible storyline could be the reader being chosen by Supreme Kaioshin to assist in a mission to save the universe. The reader could start as an ordinary being but gradually develop powers under the Kaioshin's guidance.
Another place to find such fanfiction could be FanFiction.net. However, the quality and content can vary widely. You might have to sift through a few to find the ones that really catch your interest. Some fanfictions might explore the powers of Higashi no Kaioshin in relation to the reader, like the reader getting caught up in a situation where they need his powers to survive.
A major theme is identity. Since she is a female version of Piccolo, she has to come to terms with who she is compared to the original Piccolo. Family also plays a role. In some fanfictions, she might be searching for her family or creating a new family of her own. Additionally, the theme of good vs. evil is common, as she battles against various villains.
I'm not that familiar with the specific 'Brian Piccolo Thanksgiving Day story'. Maybe it could be about how he spent the Thanksgiving Day with his family, sharing a big meal and giving thanks. It might also involve some special traditions he had on that day.