One possibility is that it focuses on a love story between Lucy and Rufus. They start off as rivals, perhaps competing in a magic competition. But as they get to know each other better, they realize they have more in common than they thought and fall in love. This could involve them sharing their dreams and fears, and overcoming obstacles together to be with each other.
The magic system in Fairy Tail should be well - represented. Since Lucy uses Celestial Spirit Magic and Rufus has Memory - Make Magic, there could be interesting battles or challenges where they combine their powers. For instance, Rufus could remember a weakness in an enemy's magic and Lucy could summon a Celestial Spirit to exploit that weakness.
Perhaps in a fanfiction, Rufus and Lucy find themselves in a parallel universe where their guilds are enemies. They have to fight against each other at first, but as they learn more about the other's situation, they start to question the enmity between their guilds and their relationship takes an unexpected turn. For example, they might secretly work together to find a way to restore the original state of their worlds.
Suppose there's a powerful dark magic user they have to face. Rufus could use his magic to quickly analyze the opponent's weaknesses based on his vast memory of magic users. Lucy could then summon the appropriate celestial spirit to target those weaknesses. For instance, if the enemy is weak against water - based attacks, Lucy could summon Aquarius. And Rufus could keep feeding her information about the enemy's movements and possible counter - attacks during the battle.
A good Gray x Lucy fanfic often has strong character development. It should show how their personalities interact and change over time. For instance, Gray's stoicism might crack a bit in the presence of Lucy's vivaciousness. Also, the plot needs to be engaging. It could be a new adventure that forces them to rely on each other, like facing a powerful dark wizard together. This way, their relationship can grow organically within the story.
One great Gray x Lucy fanfic is 'A Chance Encounter'. It beautifully portrays their relationship development. The story starts with an accidental meeting between them during a mission. Gray's cool and collected nature contrasts with Lucy's more emotional side, and this creates some really interesting interactions. As the story progresses, they start to rely on each other more and more, and the author does a wonderful job of building the romantic tension between them.
Some great 'fairy tail natsu x lucy fanfic' stories include those where they go on a journey to a new land. In these stories, they face new challenges together and their bond grows stronger. For example, there's a fanfic where they have to save a magical kingdom and in the process, their relationship evolves from friendship to something more. Also, there are fanfics that are set in an alternate universe where the events of the original Fairy Tail are different, but their connection remains at the heart of the story.
A good one has well - developed characters. Natsu and Lucy should be in - character, with their personalities intact from the original series. For example, Natsu's impulsiveness and Lucy's determination. The 'lemon' part should be tastefully done, not just gratuitous. It should add to the relationship development between them.
There is also the theme of discovery. Lucy discovers more about the Dragon Slayers' pasts and their powers, and in turn, they learn about her celestial spirits. This mutual discovery helps to strengthen their relationships. Additionally, the theme of protection is common. The Dragon Slayers often find themselves in the position of protecting Lucy, which shows their care for her and also the importance of her role in their group.
One common theme is his growth as a character. Many fanfictions explore how Rufus can develop his magic skills further and become more powerful within the Fairy Tail universe.