One day, there was a legendary trainer named Terry. Here is his adventure.

It was time-Cardos. It was time.
Terry dashed to Prof.Leaf's house, and said:
"Hi! I'm a beginner!"
Leaf said "Hi! I've got a Pokémon for you! Ratting!"
"YES!" Terry shouted.
"Sssh! Paul's in bed!" Leaf hissed.
Terry began his quest, and met a Poochyena.
"Go, Ratting!" Terry shouted. "Use Bite!"
"Pooch!" Poochyena woofed.
Bite hit!
"Go, Pokéball!" Terry shouted.
It worked!
"All right! I got Poochyena!"
Next time, Terry meets Paul's Lizzing! To be continued...

I need to know two things, just so I can put things in perspective: how old are you and when did you start writing? That said, let's move on shall we? It's clear that you have not been writing for long, which isn't a bad thing, but it can make things hard for people who want to help you improve. You're probably going to bristle at what I have to say, but try to breathe and think before you reply.

There is absolutely no description, and that's not a good thing. Your story is happening in your head; you know what everything looks like, but we don't. As a writer, your job is to make it clear to us what is happening. That way, we can enjoy the world you've created as much as you do. I don't know who's who, what they look like, or where they are. "Hi! I'm a beginner!" isn't good dialogue either. Think about the way that you talk everyday; there shouldn't be too much of a difference depending on your dialect. No one talks like that, it's just not natural. If Ratting and Lizzing are made up pokemon then I highly suggest you drop them. Not only do we not know what they are, unless you posted them in the Fake Pokedex that can be found in the Fan Art forum you might get away with it and only on one very strict condition: that your reader must have looked at the entry. Do not make that assumption! If you insist on using your fake pokemon then make sure that you describe them, in words. A sprite is all well and good in an apendix, but that doesn't let you get away with not writing a description. Your story has no flow what's so ever. A scene ends every few lines before it jumps to the next one. Watch the animated series and pay close attention to the battles. It's not so cut and dry as the game makes it. Action scenes are meant to be dramatic, so do it. Why do I care about any of the characters? I don't have a bond being created with any of them. I don't feel connected to any of them, so I'm not going to care about them. You use exclamation marks too much. Descriptive text would allow you to have the same effect without so many exclamation marks. There are other issues but I don't feel like getting into it right now.

Overall, very dull, choppy and needs a lot of work. Read some of the stories on here, some have been wonderfully written. Put the effort into writing something wonderful, and I'm telling you that this is not it.