Caulifla could be a great choice. She's strong - willed and has a passion for fighting. Her energetic personality could create an interesting dynamic with Gohan, who is more reserved in some ways.
One idea could be that the Saiyan male OC is a warrior from a different part of the Saiyan planet. He meets Kale during a universal tournament. At first, Kale is shy and reserved around him, but as they train together for the next rounds of the tournament, they start to develop feelings. The OC could teach Kale some new Saiyan fighting techniques that she hasn't seen before, which helps her gain more confidence in herself not just as a fighter, but also in her relationship with the OC.
One common theme is power combination. Since Naruto has his own set of ninja powers and the fem saiyan has her saiyan powers like ki blasts and super strength, stories often explore how they combine their powers to defeat stronger enemies.
The main characters are Goku, who has always been at the forefront of battles in the Dragon Ball universe, and the Saiyan Queen. The Saiyan Queen could be a character with her own set of powers and a complex backstory. Maybe she was once a great leader among the Saiyans but had to go into hiding or something. And Goku's presence in her life stirs up new events and emotions.
One possible plot could be that the Saiyan Queen is from a different part of the Saiyan planet that was long forgotten. Goku discovers her existence while exploring the remnants of the Saiyan world. She has a unique power that Goku is intrigued by. They train together and end up changing the future of the Saiyan race.
A plotline could involve a prophecy that only a Saiyan - like Naruto and Anko can fulfill together. They start off as strangers but as they embark on the journey to fulfill the prophecy, they learn about each other's strengths and weaknesses. Along the way, they face numerous challenges, both physical and emotional, which strengthen their bond and ultimately lead them to their destiny.
One possible plot could be that the Saiyan princess, perhaps a long - lost relative of Bardock, discovers his story and becomes determined to avenge his death. She might travel through different planets in search of the ones responsible for the destruction of Bardock's team.
Well, one possibility could be that Naruto, with some Saiyan powers, has to protect Kushina from a new and powerful enemy. Maybe he uses his Saiyan strength and speed along with his ninja skills to keep her safe.
Well, it could be about Naruto having Saiyan powers and attracting a harem. Maybe he uses his Saiyan strength to protect the girls in his harem from various threats in the Naruto universe. For example, he could fight off rogue ninjas with his enhanced speed and power.
To develop their relationship, start with small interactions. For example, they could exchange fighting techniques. This would allow them to see each other's strengths and respect each other. Then, put them in situations where they have to rely on one another, like being trapped in a dangerous place. As they work together to escape, their bond will grow. Also, have them share their pasts. The Saiyan can talk about his Saiyan heritage and Android 18 can share her experiences as an android. This will create a deeper understanding between them.