I am relatively new to stock photography and still don't have that many photos on Dreamstime, but you can learn alot from the site and increase your selected photos. I use to shoot photographs and submit those I thought might be accepted here at Dreamstime. Now when I shoot I think about setting up shots strictly for stock photography. Through other blog entries and studying photographers with large portfolios, I am learning to be a better stock photographer and I am increasing the number of accepted photos.
While my progress is slow, I am happy with my accomplishments. I now take my camera with me everywhere and shoot, shoot, shoot!