He might use his ninja skills in a unique way. For example, his Shadow Clone Jutsu could be used for various tasks like exploring dungeons simultaneously or confusing the enemies in the Final Fantasy world which often have complex battle systems. Also, his Rasengan could be a powerful attack against the magical creatures there.
He could fit in as a hero. Just like in his own world, he would fight against the evil forces in Final Fantasy. For instance, if there was a dark sorcerer threatening the land, Naruto would step up to protect the innocent. His ability to make friends easily would also help him gather allies from different parts of the Final Fantasy world.
In a Naruto and Final Fantasy Lulu Lemon fanfiction, the story could start with Lulu researching a strange energy signature. This signature turns out to be related to Naruto's chakra. She then uses her magic to open a portal and bring Naruto into her world. Naruto, being the curious and adventurous type, quickly adapts to the new environment. He and Lulu then embark on a journey to discover the source of this strange connection between their two worlds.
They could be brought into the world through a magical portal. Naruto's energy and positive attitude would be a contrast to the often - darker tone of FF7. Gaara, with his calm and powerful presence, could be seen as an ally by some of the FF7 characters. They might start by helping the people of Midgar, using their ninja skills to deal with the Shinra soldiers or the various monsters that lurk in the slums.
A possible fanfiction could involve a fusion of the two worlds' power systems. The characters from both Naruto and Final Fantasy 13 could exchange knowledge about their abilities. For instance, the summonings in Naruto could be related to the Eidolons in Final Fantasy 13, and they could find ways to combine their powers for a greater good.
One idea could be to have Naruto characters in the world of Final Fantasy 10. For example, Naruto could be a Blitzball player, using his speed and agility. Sakura could be a healer, like a White Mage in Final Fantasy 10. They could be on a quest to stop Seymour from achieving his evil plans, with Naruto's Rasengan being a powerful attack against the fiends in Spira.
One idea could be to have Naruto characters in the world of Final Fantasy 15. For example, Naruto could be a guest in Noctis' group. He could use his ninja skills like shadow clones to help in battles against the daemons in Final Fantasy 15. His chakra could be seen as a new form of magic in that world.
He'd bring unique combat skills. Naruto's ninjutsu would be a novelty in FF12's world. His ability to jump high and move quickly would be useful in battles. Also, his positive attitude. Naruto is known for his optimism, which could lift the spirits of the characters in FF12.
The ninja villages might be replaced by the different cities in Spira. The concept of the Hokage could be transformed into something like a high priest or elder in Spira's religious hierarchy. The Chunin Exams could be replaced with a Blitzball tournament or a pilgrimage to gain power. And the shinobi tools could be replaced with Final Fantasy 10 weapons and magic.
Don't forget about the world - building. Describe how the two worlds blend together. Are there new locations that are a mix of Naruto and Final Fantasy elements? How do the cultures interact? By paying attention to these details, you can create a really interesting and immersive fem Naruto Final Fantasy fanfiction.