Sorry, my answer may not be accurate. As a fan of web novels, I don't have the experience or ability to read novels or understand the genre of novels. But according to the information I know, gal usually refers to a type of video game in Japan where players play a role in the game to talk and interact with other players.
Although there are many excellent Japanese gals, they are usually not group dramas because they usually tell the story from the perspective of a single character. On the contrary, group dramas usually referred to telling a story from the perspective of multiple characters. These characters were connected to each other to form a whole.
Of course, this is just some information I know. If there are other questions, I will try my best to answer them.
Another theme is self - discovery. As the story progresses, the characters learn more about themselves and their feelings. For example, the main character may find out things about his own capacity for love and commitment that he didn't know before. It's a journey of growing up in terms of emotions.
In 'My First Girlfriend Is a Gal' story, we can expect to see the development of the relationship between the main character and his girlfriend. There could be challenges they face together, such as dealing with friends or family reactions. It may also show how they grow as individuals through their relationship, learning about love, trust, and communication. The story might be filled with sweet moments, like sharing secrets or small gifts, and also some not - so - smooth times, like misunderstandings, but ultimately it's about the journey of this first relationship.
First, think about the aspect of Gal Gadot that you admire the most. Is it her role as Wonder Woman? Her beauty? Her charisma? Then, come up with a basic plot. For example, if you love her as Wonder Woman, you could start with a situation where she has to face a new threat in Themyscira. After that, create some interesting characters to interact with her. Don't forget to give her some challenges and let her use her unique qualities to overcome them.
Fanfiction based on 'hajimete no gal' could potentially focus on different scenarios. It might explore alternate storylines for the main characters. For example, it could be about the characters in different settings like a school trip or a festival, and how their relationships evolve in those new situations. It could also be about creating backstories for the side characters that are not fully explored in the original work.
I'm not sure specifically what 'hajimete no gal fanfic' is about without more context. It could potentially be a fan - created story related to a 'gal' character or concept from a particular anime, manga or game.