[Not Safe For Adults]

Introduction and Plot:

Immediately you begin by describing your main character. I was glad to see this as often times people don’t describe their characters at all, leaving the reader clueless for the rest of the story. However in the future try to incorporate these details through showing versus just telling the reader about it. For this story though, I think what you did works just fine.
I’m also glad that you described the Squirtle’s appearance, as it is just as important to describe the Pokemon as it is to describe the human characters, even if this is a Pokemon forum. :P

As for the plot, it was very simple. This is fine for a Pokemon like Magikarp but if you choose to go for more difficult Pokemon in the future, try to use more complicated plot lines than the usual ‘go out and find a Pokemon’ scenario.

Description:

You did well with the description of the characters and the main character Amelia’s clothing. I also liked that you incorporated the setting into the storyline by mentioning the effects of the rain and mud in the battle.

The biggest thing you can improve on is giving the reader details about the characters by incorporating them with actions. For instance, if you want to describe Amelia’s hair you should not just say what it looks like outright, but give a description of it while Amelia is doing something. Perhaps Amelia is pushing her blonde hair out of her face because it often gets stuck behind her bulky hipster glasses and gets in her eyes. If you give details in that way, the reader will learn more about the character and will have more interest in the character as a person due to a factor of relatability. Also, it becomes more like a story and less like a list.

Other than with your descriptions of Amelia at the beginning of the story, you did use this technique well, especially when describing the battlefield.

Grammar:

Just a few errors that I found, overall you really know your stuff when it comes to grammar.

She stood there, shouting “SQUIRTLE,” until a small blue turtle came rushing up to her.

The grammar on this is mostly correct, the only problem is the usage of commas. Here is what I would do to correct the sentence:

She stood there shouting, “SQUIRTLE!” until a small blue turtle came rushing up to her.

I added an exclamation point because she is shouting, and also because you can use exclamation points and question marks during dialogue without ending the overall sentence. Also in this instance you do not need to put a comma after the dialogue:

“Squirt...?”, questioned the Squirtle.

It replied with 'Squirt,' the girl slipping on her black shoes rimmed with faux Arcanine fur and opening the door.

^This sentence is a run-on. Basically the sentence should be ended after the dialogue. Also the ‘slipping’ and ‘opening’ parts do not fit with the rest of the story’s tense, which is past tense.

It replied with, “Squirt.” The girl slipped on her black shoes, which were trimmed with faux Arcanine fur, and opened the door.

Also, there is a difference between it’s and its. It’s is a shorter form of it is and its is possessive. Those were the only errors I found though. Good job.

Battle:

Great job on this! Using the setting to affect the outcome of a battle is a great technique that gives higher stakes to the situation. I also commend you on making the battle two-sided instead of having Squirtle be a complete powerhouse in comparison to Gothita.

Just note that you do not necessarily need to have a battle in order to catch a Pokemon. In this case, it did seem a little iffy to have a battle with a different Pokemon than the one you captured, especially since you didn’t mention Magikarp at all until the very end. Since it is your first story though, I’ll let it slide. Besides, a battle with a Magikarp wouldn’t have been nearly as interesting. :p

Overall: I think that you are a great writer. You already know a lot about grammar and writing as a whole, you just need to fine tune it a bit. As long as you continue to practice your writing you will definitely be amazing, I just know it. Magikarp captured!