In this fanfiction, it could be that Ash has a really good strategy. He might first make Gyarados use up a lot of its energy by making it attack Charmander's illusions or decoys. Then, when Gyarados is tired, Charmander can step in with its full power. Charmander could also use the environment to its advantage. Maybe there are some flammable objects around that can be set on fire by Charmander, creating a more powerful and widespread fire attack that Gyarados can't avoid.
Ash's character development is quite significant. At first, he might be a bit over - eager and not fully understand Charmander's needs. But as they spend time together, he learns patience. He realizes that Charmander can't always be pushed to its limits right away. His confidence also builds. When they win battles together, he starts to believe in his own abilities more. And his sense of loyalty deepens as he would do anything to protect Charmander.
A key element is the bond between Ash and Charmander. It's usually shown as a strong and unbreakable connection. Another is their growth. Ash grows as a trainer and Charmander as a Pokémon. For example, Charmander evolving into Charmeleon and then Charizard is often a big part of the story.
One possible plot could be that Ash finds Charmander much earlier than in the original series. They could form a really strong bond quickly and start training in a different way. Maybe they focus more on speed and stealth rather than the usual battling approach at first.
One great fanfiction could be 'Ash as a Female: The Charmander Adventure'. It follows the female Ash as she embarks on her journey with Charmander. It's full of exciting battles and heart - warming moments between Ash and her Pokémon. The author does a great job of portraying Ash's determination in a new light.
You can try fanfiction websites like FanFiction.net or Archive of Our Own. Just search for 'ash charmander' in their search bars, and you should get a list of relevant fanfics.
It would change his journey a great deal. Firstly, having a shiny Charmander would make him stand out more. Other trainers would be more likely to challenge him, either to prove themselves against someone with a rare Pokémon or to try and get his Charmander. Also, trainers with more experience might offer to help Ash train his shiny Charmander, which could lead to new training techniques. In Pokémon contests, his shiny Charmander would be a show - stopper, giving him an edge in those aspects of his journey as well.
You can try fanfiction websites like FanFiction.net or Archive of Our Own. Just search for 'Ash starts with Charmander' on their search bars and you might find some interesting stories.
The plot could involve Ash starting his journey in a unique way. Since he has a shiny Charmander, it might attract the attention of Team Rocket more than usual. They could constantly try to steal it, creating many action - packed chase scenes. Ash would have to train his Charmander to be stronger to fend off these threats. Along the way, he could meet other trainers with rare Pokémon who are both friends and rivals, all while aiming for Pokémon League championships.
There is also a 'ash gets charmander fanfic' where Ash finds Charmander in a very different scenario than in the original series. Maybe in a more desolate area, and this changes their dynamic as they start their adventure. It might focus on how Charmander's presence affects Ash's growth as a Pokémon trainer on an emotional level.