As Rainbow Dash trains excessively for the Equestrian Grand Prix, she receives a letter from Applejack to help her look for Applebloom who has gone missing. Rainbow decides to first take part in the competition then head over to Sweet Apple Aces. As it turns out the other ponies eventually found Applebloom, however she was dead. Rainbow Dash blames herself for the tragedy that happened that day and the guilt begins to eat her away. Rainbow Dash can't take it anymore and decides to go see Twilight for a spell that might help her. The spell requires Dash to fall asleep, but when she does she wakes up in Cloudsdale. This is not the same city as before though, it is abandoned and has strange creatures lurking about. With mysterious notes located around, Rainbow Dash's only hope is to follow what the clues say and hope for the best.
First Chapter to my first story, Yeah I don't mind you guys telling me what to change or what to improve on. I need to improve after all lol
It's... Well, alright I'll just get right down to brass tacks; it's rushed, and sloppy. You've got Rainbow practicing in one paragraph and then in the next one she's reading AJ's letter. Also Rainbow just straight brushing off Applebloom's disappearance doesn't seem fitting for the Element of Loyalty, and her doubting in only one sentence that they'll find her doesn't absolve it of the fact that she still brushed it off with almost no hesitation.
Your spelling and grammar are fine, but you've got walls of text going on like nobody's business. When ending a paragraph make sure there's a space between it and the next one. As for the story itself I'm getting a Silent Hill type vibe from the description and I'm eager to see where you'll take the story.
Suggestions? Okey-dokey-lokey!
1) Slow down a little. Add some details and take your time to build the scene and its characters. The clearer the picture you paint, so to speak, the more the reader will be drawn in.
2) Text walls are not reader-friendly. If you're unfamiliar with that term, it means your paragraphs are squished together. Add an extra line between them (like CodenameOne said) or indent (there's a button that does that when you're editing your story), or both.
3) As already noted, Dash dismissing Applebloom's disappearance is pretty out of character. She represents Loyalty, after all, and she rejected her dream job in the second episode because it meant abandoning her friends in their time of need. You might be able to make it work if you give Dash more of an internal conflict, but it's still a little risky.
Hope you find that helpful. Good luck!