Survival is a very common theme. Just like in the original Hunger Games, in 50th Hunger Games fanfic, tributes have to find ways to outwit and outlast their opponents. They might have to deal with harsh environments and limited resources.
A boy from District 4 who is an expert fisherman. He's not just physically strong but also very clever. He could use his fishing skills to catch food in the arena and also use the fishing nets as weapons or to set traps for other tributes. His backstory could be that he wants to win the Games to bring pride back to his district which has been overlooked in recent years.
One idea could be to focus on a new kind of arena. Maybe an arena that changes based on the tributes' fears. For example, if a tribute is afraid of water, parts of the arena would flood when they're nearby. Another idea is to create a group of tributes who form an alliance not for survival, but to rebel against the Capitol from within the Games.
Some fans might also like the mentors in the 77th Hunger Games fanfiction. They are the ones with the experience of past games, and they use their knowledge and wits to guide their tributes. Their complex personalities, as they balance their loyalty to the Capitol and their care for the tributes, can be really interesting to explore.
One interesting plot could be a new type of alliance formed between the tributes. For example, tributes from different districts who share a common skill, like hunting, come together not just for survival but to change the rules of the game from within.
One main character could be a young girl from District 9, who is really intelligent and uses her wits to survive. She might form an alliance with a boy from District 12, who is known for his speed and agility. They make an unlikely duo but their combined skills help them in the games. There could also be an older tribute from District 7, who has a lot of experience in the forests and uses that to his advantage in the arena.
Another interesting angle is to explore the backstories of the Gamemakers for the 50th Hunger Games. What led them to design the particular challenges in the arena? Were there any internal conflicts among them? This could provide a deeper understanding of the whole Hunger Games concept in the context of this specific event.
A previous victor forced to return to the Games for the 50th edition could be a great main character. Their experience from the past would give them an edge, but also a lot of emotional baggage. It would be interesting to see how they handle the new challenges and younger opponents.
A girl from District 11 who is an expert at climbing trees and has a strong sense of justice. She could be one of the main characters, using her skills to survive in the arena and also standing up for the weaker tributes.
A young girl from District 12 who has been secretly training in combat skills her whole life. She could be the main character, using her wits and skills to survive the games.