About 15 years go, and after a couple of self-published strips, I started Blurb. It was a simple story involving street artists who lived in a fictional town. I had a family of characters which I'd developed over a while, and populated the story with music and art references from all over the map.
The story itself wasn't too coherent, but, it was done in one page installations, that continued a basic plot involving thugs, freight trains, and UFO's. At the time, I'd contributed to a couple of magazines, and submitted the comic strip as one off's. I got some positive feedback, although one person had admitted to me that thought a little kid had drawn it.
Best of all, I'd gotten up the nerve to submit it to Fantagraphics for publication. Below is the rejection letter I got a couple weeks later. I did learn a lot from feedback like this, and, started a second iteration of the strip and characters a few years later.