Friendship is a very common theme. Since in the My Little Pony world, friendship is highly valued. Their relationship often starts from a place of rivalry or misunderstanding, but through various events, they become friends. For example, they might help each other in a magical quest or face a common enemy together.
There's also 'Starlight and Trixie's Journey'. In this fanfiction, it focuses on how they both help each other overcome their personal insecurities. Starlight Glimmer's past issues with controlling others and Trixie's need for constant attention are addressed. As they work through these problems side by side, their bond strengthens in a really interesting way.
Some fanfics might have a theme of self - discovery. Both Starlight Glimmer and Trixie have their own insecurities and areas for growth. In these fanfics, their relationship with each other helps them to discover more about themselves, like Starlight learning to be more confident from Trixie's bravado or Trixie learning about the importance of true friendship from Starlight.
One common theme is friendship development. They start as acquaintances or even rivals and then gradually become closer friends or more. Another theme could be adventure. They might go on an adventure together and through that, their relationship deepens. There's also the theme of self - discovery, where they help each other figure out things about themselves.
You can start by looking on popular fanfiction websites like Archive of Our Own (AO3). There are often a large number of fanfictions about various pairings, including Starlight Glimmer and Trixie Lulamoon. Another option is FanFiction.net, which also has a wide selection. Just use the search function on these sites and type in the relevant names.
Another option is to join some My Little Pony fan communities, such as on Reddit or Discord. Members often share and recommend their favorite fanfics. They might be able to point you in the direction of some great Starlight Glimmer x Trixie fanfics that you wouldn't find easily on your own.
Magic is also a big theme. Given that they are both magic - users in the MLP universe. Fanfics often explore new magic spells they discover together or how they use their magic to overcome challenges. Sometimes they might even compete in magic contests within the story.
One great MLP Starlight Glimmer fanfic is 'A New Beginning for Starlight'. It shows her journey of redemption in a very interesting way. The character development is well - written.
Redemption is a common theme. Since Starlight Glimmer had a past of being a bit of a villain, many fanfics focus on her journey to make up for her past mistakes and become a better pony.
Friendship is a very common theme. Since they are friends in the MLP universe, fanfics often explore how they support and grow with each other. For example, in many stories, they help each other through difficult times.