I'm not sure about specific 'rainbow dash x scootaloo fanfic' but you can try searching on popular fanfic websites like FanFiction.net or Archive of Our Own. There might be some interesting stories there.
One common theme is mentorship. Rainbow Dash often acts as a mentor to Scootaloo, helping her with flying and other aspects of life. Another theme is friendship. They develop a strong bond that goes beyond just a normal acquaintance.
Friendship is also a major theme. Their relationship is explored in different ways. Sometimes it's about how they support each other during tough times. Like in some fanfics where Scootaloo gets bullied for her lack of flying ability, Rainbow Dash is there to cheer her up and encourage her.
One great fanfic could be about Rainbow Dash taking Scootaloo on a special flying adventure. It might include Rainbow Dash teaching Scootaloo new flying techniques. This would strengthen their bond and show how much Scootaloo looks up to Rainbow Dash.
In this fanfic, it could also explore the relationships between the three characters in different settings. It could be set in Ponyville, where they face daily challenges together. Or perhaps they go on a journey to a far - off land, and along the way, Scootaloo learns more about herself and her new family. There could be conflicts too, like when Scootaloo has to choose between following Twilight's studious ways or Rainbow Dash's more adventurous path.
Good character development. Show how Scootaloo grows in confidence with Rainbow Dash's help. Also, an exciting plot. Maybe something that involves flying challenges or a mystery to solve. And of course, the friendship between them should be at the core, like how they support each other through tough times.
Friendship is also a big theme. They share a special bond that is explored in many fanfics. For example, they might support each other during tough times or celebrate each other's achievements. It shows how their friendship enriches both of their lives.
A good fanfic in this regard often has a strong emotional connection between the two characters. It could be about how Scootaloo overcomes her insecurities with Rainbow Dash's support. This shows the power of their friendship.
You can start by looking on fanfiction websites like Fimfiction. It has a large collection of My Little Pony - related fanfictions, including those about Rainbow Dash and Scootaloo. Another option is Archive of Our Own (AO3). It also has a wide range of fan - created stories in this category.