Upload & Sell: On
Okay, now this thread has gotten confusing beyond belief, especially for someone sort of starting out. To the original poster, please, please, disregard the post above with the two test images. Neither of them will do you any good and in fact, both, for very different reason, will lead you far astray.
The first image, while meaning well I'm sure, fails the first color management test. It's an untagged RGB image with no embedded profile. That means it will display differently depending on how your particular copy of Photoshop is set up. Not good for helping you judge anything at all.
The second test file is Andrew Rodney's ancient and outdated (and rather mediocre) test image. The primary problem with this test file is that it's in a color space that virtually no one is using today. In the very early days of Mac color management, Colormatch RGB was sort of a standard but sRGB has replaced Colormatch as the defacto color standard. A lot of online printers expect sRGB and if you send this file, those printer will often ignore the embedded profile and assume sRGB, which has a completely different gamma. This was an okay file a dozen years ago, but not so much today.
It doesn't matter if you're going to print or just post images online, you still absolutely need to calibrate. You want your images to be right, and the very best way to do that is with a hardware calibration device. It's the best couple of hundred dollars you can spend. The best bang for the buck is the X-Rite i1Display Pro.