Well, you can try searching on some popular fanfiction websites like Archive of Our Own. There might be a variety of stories with that theme. Just type in 'gray becomes a dragon slayer' in the search bar and see what comes up.
One common theme is the power struggle. Gray often has to deal with his own powers as an ice dragon slayer and how to control them better. Another theme is friendship. He usually has comrades who support him in his battles.
It's also likely that Naruto becomes a god dragon slayer as a result of a prophecy. The fanfiction could explore how he initially struggles with this new role. He has to deal with the expectations that come with being a 'god' - level dragon slayer. Along the way, he might make new allies, like other dragon slayers or magical creatures who recognize his potential and help him in his journey to master this new power.
Maybe Gray has to team up with a dragon in order to defeat an ancient evil that threatens to destroy the world. The dragon could have its own motives and Gray has to figure out if he can trust it.
One great 'Gray Ice Dragon Slayer Fanfic' could be 'The Icebound Quest'. It follows the journey of the Gray Ice Dragon Slayer as they battle against dark forces threatening their world. The story is filled with intense battles and the slayer's struggle to master their ice powers.
In the world of 'ice dragon slayer gray fanfiction', there is a story that takes place in a frozen tundra. Gray is on a quest to find a rare crystal that can enhance his ice - slaying powers. Along the way, he meets a group of allies who help him. This story is filled with action - packed battles against ice - based monsters and a lot of character development for Gray.
The unique powers. A Gray Ice Dragon Slayer has the ability to manipulate ice in amazing ways. Fanfics that explore the full extent of these powers, like creating complex ice sculptures for defense or using ice to travel quickly, are really cool.
One possibility is that Lucy discovers a hidden power within herself that is related to dragon slaying. Maybe she has a long - lost ancestor who was a dragon slayer. This newfound power could lead her on a journey to learn more about it, facing challenges along the way, like dealing with other mages who are jealous or scared of her new abilities.