Hey Michelle -
This was my journey - if it helps!
When I first started designing, I didn't even know about commercial use items. So I would search up themed items on Google, and hand-trace the shapes to make my own elements. Most of my stuff looked too digitized and I definitely OVER-used textures, bevels, etc. (just because I wanted to make the most of my program - LOL).
As I got better, my style "calmed down." I am a paper-scrapper at heart, so I wanted my digital layouts and kits to look like a paper layout as much as possible. I discovered CU items for ribbons, clips, etc. I still google themed images and see if I can re-create them myself.
I started at a very small store. Then moved to a store that was a teensy-bit bigger, and I kept refining and working to get to Gingerscraps (which was my "holy grail" of places to be). Honestly, I was told NO by GS twice before I was ready to be here! And I'm still flying high over getting accepted here!

I was told NO a lot - but I never gave up. If this is something you want to do,
DON'T GIVE UP!
I personally like "themed" kits vs. vague ones - like I'll design a basketball-themed kit before I'll try one just called "Calm & Tranquility" or something. Then I know I can make things like a basketball, scoreboard, jersey, whistle, water bottle, etc. And add the filler items (ribbons, frames, clips, word art, word tags, flowers, greenery, etc.).
This is a full-time job for me -but it doesn't not make "Full-time" money. That's something you need to know. I work on my business 6-10 hours a day and often on weekends. Designing is just a small part - because there is also previewing, packaging, advertising, blogging, newsletters, Facebook promotions, and more.
I started with Paint Shop Pro as my design program because that was the one I knew really well. Just in the last year, I've been doing half of the work in PSP, and then moving into Photoshop/CS2 to use styles. I toggle between the two programs regularly. Whatever program you choose, know them well.
I hope that helps!

Mags / MagsGraphics