Hello!
Cute as this is, I applaud you for trying to write your first fanfic. Welcome to the world of fanfiction. :)
Now first thing is first, I hate plugging in a different website's guide, but I feel
this one might be a little bit better for you in the long run than the
Writing Resources thread which is filled with lots of links. Be sure to read the
Tips on Composition section,
Characters, and
Stages. Do look at the Resources thread though if you get a chance.
For now, I'll start you off by saying you need a lot more description.
"My adventure... starts now." said a voice
Is this voice mysterious, is it deep? Where is it at? Try to include some of these things.
Also, since this is a fanfiction, '>Insert Pokémon theme tune here<' isn't going to work too well. Keep it out and just move on with your story. Same goes with the Pokémon levels. In fanfiction, it's good practice to not give levels to Pokémon because this isn't the game. You might be basing your writing
from the game, but you're telling a story here, not letting us watch you play if you understand what I mean.
Next, try to make your chapters longer. Good chapters tend to have at least 5 pages or more on Microsoft Word. If you don't have Word, download
OpenOffice or use Google documents to write your stories. (The latter you need an email to use, so I'd probably save yourself the trouble and use OpenOffice or Word.) Also remember to use your enter/return button between paragraphs so that it doesn't look squished.
In the end, you've just got to keep practicing. Pick up a book at home and read through it. Don't just read it though, look at how the author writes their story. The more you read and practice writing, the better you'll be. Post in the
beta thread and ask for a beta reader, maybe you'll get someone who will be willing to look over your story before you post it.
Keep trying, and best of luck. :)