Yes, there are many great Ash and Gary fanfictions centered around their friendship. You can find them on popular fanfiction websites. Some explore their early days as rivals and how that rivalry gradually turned into a deep respect and friendship over time.
There are quite a few. One interesting aspect often explored in these fanfictions is how they support each other in their Pokémon journeys despite their initial competitiveness. They might share tips on training or help each other out in difficult battles, which makes for a really engaging read.
Chapter 728, "Number One in the Joint Exam!", is the clearest early answer because it turns Jiang Cheng's situation into a concrete plot event. Early on, They were the first set of final exams for all graduating high school....
Chapter 899, "It's actually a seal script?!", is the clearest early answer because it turns Jiang Cheng's situation into a concrete plot event. It opens with Jiang Cheng, with his head dizzy, was pulled into the courtyard by...
Chapter 716, "Cook a Special Meal", is the clearest early answer because it turns Jiang Shixu's situation into a concrete plot event. The chapter turns that into something concrete by moving from The following week was much quieter, and Jiang Li finally had some...
Chapter 734, "Are These Primary School Students Arguing?", is the clearest early answer because it turns Jiang Zhao Yuan's situation into a concrete plot event.
Chapter 669, "My First Love Sister Who Died Young", is the clearest early answer because it turns Seeing Jiang Shixu's situation into a concrete plot event. A useful checkpoint is the way the scene starts with Bang," the door closed, but Chen Qijun's words lingered in Tai Fan's...
Chapter 611, "The House She Built is No Ordinary House!", is the clearest early answer because it turns Ji Yanbai's situation into a concrete plot event. A useful checkpoint is the way the scene starts with Jiang Li didn't care about the dissenting voices at all; she rolled...
Chapter 671, "Who Understands Family!", is the clearest early answer because it turns Jiang Cheng's situation into a concrete plot event. A useful checkpoint is the way the scene starts with Director Meng drove the shuttle bus around Jingcheng Airport.
Chapter 831, "Brother, who do you like the most?", is the clearest early answer because it turns Sister's situation into a concrete plot event. The chapter turns that into something concrete by moving from Just as Jiang Shixu finished washing up and was getting ready to...
A practical answer is Chapter 13, because it turns the idea into a concrete scene. The chapter opens with Sensing that something was off with Jiang Yan, Jiang Yan dismissed the..., adds pressure through He probably had a good guess who it was., and ends on How could this happen..." Lin Manru.
Chapter 646, "This person deserves a slap in the face!", is the clearest early answer because it turns Jiang Cheng's situation into a concrete plot event. Early on, Jiang Yan: "....." Bloody green tea, get lost!. By the end, You won't be at a disadvantage." Zhao Lang's lips curled up a bit,....