I'm not sure specifically as it depends on the fanfic. But it could be a new set of tributes from different districts. Maybe a strong - willed girl from District 4 and a smart boy from District 11.
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.
It could be about a new set of tributes. Maybe there's a tribute from an unexpected district who has a unique skill, like being able to communicate with animals. This skill gives them an edge in the arena, leading to all kinds of new alliances and betrayals.
One interesting aspect could be the new characters introduced. They might have unique backstories and personalities that add depth to the fanfic. For example, a character could be from a previously unexplored district with a special skill. Another aspect could be the plot twists. Maybe the main character forms an unexpected alliance or discovers a hidden rule in the 5th Hunger Games. Also, the fanfic might explore different themes compared to the original Hunger Games, like the impact of a certain technology on the games.
A girl from District 12 could be a great main character. She could be different from Katniss, maybe she's more of a strategist than a hunter. She uses her wits to form alliances and outsmart her opponents in the arena.
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.
There could be a boy from District 4 who is an expert fisherman. He uses his knowledge of water and fishing to survive in the arena. He might form an alliance with the girl from District 12, and together they face the challenges of the 50th Hunger Games. He is also very clever and can outwit other tributes.
One idea could be to focus on a new type of arena. For example, an arena that is constantly changing, like it shifts from a desert to a frozen tundra. Another could be to explore the backstories of the tributes more deeply. Maybe one tribute has a secret connection to the Capitol that they are trying to hide. A third idea is to have a group of tributes form an alliance not for survival in the games, but to send a message to the Capitol about the cruelty of the Hunger Games.
One great 50th Hunger Games fanfic could be 'The Rebellion in the 50th Games'. It might focus on a group of tributes who decide to band together against the Capitol in a more organized way than in previous games. They could use hidden skills and knowledge passed down from previous rebels.