Well, it's obvious you enjoy photography, and that's the most important thing
These look like the type of shots a lot of us started shooting. Unfortunately, microstock has evolved into a professional (or highly advanced amateur) medium.
If you really want to give it a shot, don't let anyone dissuade you. But you definitely have your work cut out for you.
1. The catfood. The good news is you seem to have done a good job creating a smooth path to isolate it. Bad news: It is a low demand subject with many better examples already in the stock libraries. Also, the lighting isn't right. Most of your light is on the front of the bowl, while the top part, with the catfood, is in shadow. It should be the opposite. You should have your light off to the left or right, and skimming over the catfood to give it dimension.
2. The flower - the good news is you have a nice composition, with the flower off to the right, more along the lines of Rule of Thirds, rather than dead center. Bad news - again, very low interest subject. Also, the insect inside is kind of murky and sandy and just gets lost. Very difficult to tell what it is.
3. The frog. I actually like this as a picture. It is kind of whimsical. But again, low interest subject. Also, your composition is too wide and shows too much of the boring dirt. I would crop in tighter on the frog, and maybe get down on his level for a more interesting picture.
The kinds of subjects you are shooting won't ever make it onto the stock sites, but they are GREAT for photography practice. They are readily available, and you can use them to learn about composition, lighting, and post-processing.
