The plot could start with a strange magical accident that sends Harry back in time and causes some sort of time - loop where he ends up being his own father. Then, he has to figure out how to break the loop while also dealing with the implications of his new identity.
Perhaps it delves into the character development of Harry in a unique way. By being his own father, he would have to take on different responsibilities and perspectives. He might have to reconcile his own youthful self with the more parental role he has to assume, which could lead to some really interesting internal conflicts and growth.
One possible plot point could be how Harry manages to exist in a time - loop scenario that makes him his own father. Maybe there are complex spells involved that warp time and genetics in a magical way.
The original story has a very linear family structure and a set timeline of events. But in this fanfiction, the very foundation of Harry's existence is altered. It might change his relationships with other characters too. For example, his relationship with his mother would be extremely different as he is now in a position where he has to be the one to start the family with her. His role in the wizarding world would also shift as he now has a very unique identity that defies the normal laws of nature. This could lead to new adventures and challenges that are completely different from what he faced in the original story.
He would likely use Transfiguration magic. This would allow him to shape the raw materials into the form of a staff. He could also use Enchantment spells to give the staff special powers like the ability to repel dark magic or enhance his own spell - casting abilities.
In fanfic, Harry Potter may create his own world by exploring the boundaries of magic that were previously unknown. He might stumble upon ancient spells or magical artifacts that give him the power to shape a world. He could use his connection with his friends, like Hermione's intelligence and Ron's loyalty, to help him in this endeavor. For instance, they could research together in the restricted section of the library to find ways to create new magical laws and landscapes for his world.
Another plot could be that Harry, while living alone, stumbles upon a mystery in his own neighborhood. He starts to investigate it secretly and uncovers a conspiracy within the wizarding community that could potentially change the whole magical world. He has to use his wits and the skills he has learned over the years to solve the mystery and save the day.
Well, he might first search through old wizarding shops in Diagon Alley. There could be some ancient and forgotten stashes of rare materials. He could also ask Hagrid for help. Hagrid has a great knowledge of magical creatures and their habitats. Maybe there are some creature - related materials that could be used in the staff. For instance, the feathers of a phoenix or the horn of a unicorn (assuming it's done in an ethical and legal way in the context of the fanfic).
Well, he might finally have some privacy to study magic without distractions. He could decorate the room with his favorite Quidditch posters and pictures of his friends and family.