I've gone through your story and I've done some grammar corrections for you. They appear in bold below.
Journey of a Life Time: Sinnoh Legends
Written by Anonymous
Prologue
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The thought of a new Pokemon journey or one that is yet to begin is like finding a whole cave of precious jewels and diamonds for Lindsey! Liz, along with friends will set off on a long and “memorable” journey, aiming to become the best. Along their adventure, they will encounter dangerous plots by the evil, legendary Pokemon, and an ever-lasting amount of fun and excitement. Liz’s journey will start now as it ends in other regions, say Hoenn! So behold the great story I shall tell about this one young lady!
Chapter 1
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Rise and Shine! I woke up to the smell of fresh air, leaping into my bedroom. Today would be the day. The day I
start my Pokemon journey! The day all my memories from my childhood
begin to relive. The time has come, at last! I got up from my bed and looked out the window, seeing the beautiful mountains and the birds bathing in the little fountain below me. Here
was a sign that this day will be full of luck and fun. “Liz! Are you in your clothes, yet? You need to get out of your pajamas!” my mom’s
voice boomed through the echoing hallway, disturbing the beautiful sights and sounds
I was seeing and hearing, breaking the silence. It all slowly faded away as
my strict-looking mom stepped in.
“Look at your room! It’s usually so clean! And now that you’ve
turned ten, you think that you can be so messy, don’t you! Well, you won’t be going anywhere
past that door until all this is cleaned up!” she barked. Having a step-mom was miserable. She expected you to call her the lovely and soothing word of “mom” and simply acts like a devil. Why did she have to do this to poor me?
“Mom, I just had a sleepover the other day! Do
you actually expect me to have it cleaned up in just one day? It was my birthday party with all my cousins yesterday!”
“Lindsey Hayes! If you don’t clean up this room and rinse your mouth so you won’t be talking back to me, you’re so not going to Professor Rowan’s lab today!”
“Fine! I guess it’s time you learned a lesson! Two can play
at that game!” I murmured.
It was exactly
forty seconds later when I walked out into the dining room, dressed casually and not so “Miss Perfection” like my “so-called-mom” likes me. I looked cooler, wearing a cute pair of jeans and a little three-laced tank top. On my head was a cute little headband. Mom looked at me as if I was crazy for a moment, but then she looked pleased. Wait a minute, Mom being pleased?????? That
was just odd! Totally odd! “Lindsey, so you’ve finally decided to come down for breakfast? We will be groundi….grounding…..Hahahah.” she laughed. “I cannot keep on holding my breath anymore! All these years, I only pretended to be mean and strict, wanting you to grow up being strong and responsible. But today, I cannot keep going! I have to laugh out loud! It’s too hard to keep on bossing you around! Oh, Dad and I have a little gift for you! It’s your own, new bike!” My eyes shone with amazement. This
couldn’t be actually happening. That was when I had the urge to run up and hug her. Plus,
Dad was finally home from his trip to Paris!
“Good bye, Honey!” Mrs. Hayes waved, along with her husband, as I got onto my brand-new teal bike. This
was going to be great! I’m heading to Twinleaf Town, finally, and
I'm about to start my Pokemon journey! What
was about to behold
was yet to come. But little did I know, above me stood two snow-white clouds, in the shape of Palkia and Dialga. If I’d seen that earlier, I would have known that this one day would be the best of them all! Oh, am I excited about what lies ahead of me! ^___^
Well, it's not too bad; however there were a few things I noted about it.
First, the prologue isn't really a prologue, more of a really brief introduction. A prologue should be something interesting or suspenseful, something to draw in readers.
Second, paragraphing works a little different on these forums. To properly separate the fic into paragraphs, you need to press Enter twice so there is a blank line between paragraphs. Also, whenever a new character speaks, you need to start a new paragraph.
Third, I find it interesting that you're writing in first person, but it is a harder point of view to write in. And there are a few places you mix up present and past tense. I changed most of them to past tense in my corrections above.
Next, you don't really describe your characters all that well, so I can't visualize what's going on. You don't need a whole lot of description, just enough so that readers can visualize the characters and scenery in their head.
Finally, a couple of plot-related things. First, the change in the stepmother's attitude just seemed... weird and abrupt. I don't know, the change just seemed strange to me. Secondly, so far you've got the standard journey-fic plot here. While I don't have a problem with journey fics, some other reviewers will warn you that they've seen this before. Basically, just make sure you try to add something truly unique to your story, so it stands out from everyone else's. And lastly, try making your chapters just a bit longer so more action and character development happens in the chapters.
With all that said, I do see a lot of potential with your fic and your writing. Good luck on the next chapter, and let me know if you want any help!