Don't get pissed off when a prof says he doesn't like the colours you picked. The lessons you think are most useless tend to be the most helpful in 4 years time.
Work up a good portfolio, if it's for getting into school something diverse, if work show them you can do a myriad of things, but related to one field so it's apparent you are pro at this thing you do.
On a small note, there's a difference between being a pro and an expert. A professional is someone who does a specialized task for money. That's it. An expert is someone who is proficiently skilled at a specialized task. The average time it takes to master something is 7 years, give or take a couple years based on how hard you work at learning and practicing.
Don't try to get ahead of yourself. Anything you try to make now will be completely different in terms of quality and execution than your skill level by the end of college and judging by your gallery, you've got a long ways to go. Experiment and practice things on your own to help improve your skills and understanding of graphic design and illustration. Start with some tutorials making things in Adobe Illustrator and/or Photoshop so you understand the programs well. I also highly recommend you draw a LOT. I write down ideas and sketch things all the time, because it really helps you flesh out ideas. Don't jump straight to the computer to design something unless you already know exactly what you're making. Pick up a few books on graphic design to introduce yourself to the many things you'll need to know about design. I recommend you get this book: [link] You can also find some online sources that have this book as a PDF.
A designer must have an eye for good design, so the best thing I can tell you is to train your eyes to identify good designs and examine their details for your own practice. Think about why that one design looks so good. What makes it stand out? Is it the combinations of colors? The use of patterns? Is it the typography? To learn more about what makes a design good: [link]
My Graphics and Design teacher has told me that a strong portfolio is key to getting a job. You should have some variety in your portfolio too. Having a variety of work shows your skilled in more than one area.
Also when going for an interview for a job, dress neat and act respectful. A decent portfolio won't get you a job, if you have terrible manners.