I've been on DreamsTime and in the stock world for six months now and have a number of thoughts of the experience so far.
First of all, it seems the sky is the limit. You look at the successful portfolios and find inspiration with them; if they can do it, you can do it. Getting there is another story. "There" is something you have to define for yourself. When my portfolio reached about 50 images, that is when the sales really began coming in. I don't want to make it sound like a lot of sales, but 7-10 sales/month seems to be a lot for 50 images. For me, then, and if you assume sales will be linear in proportion to portfolio size, 500 images will equate to 100 sales/month. (I doubt if sales will be linear to portfolio size but being successful with 50 images means you should see much more success with 500 images).
The goal for now then is to get to 500 images.
However, I am not a full time photographer, I have a day job like most. I do not have a studio nor do I have plenty of beautiful people lined up who are willing to model for me. This has meant trying different things and getting beat up pretty bad with the review process. It seems reviewers prefer only images that fit a rhetorical stereotype of pretty girls holding shiny toasters. The sales I have been getting with my type of portfolio proves the stock world is hungry for images beyond the accepted norm. It has been a challenge to convince others of this. I have had made sales with images that were rejected and then accepted after appealing. Still, it has been a difficult road to make people realize there is a great potential of revenue for images that are outside the box.
This is an image that sold despite not being "normal" stock:
Regardless of the definition of what can be considered "STOCK," my photography has greatly improved in a short period of time. I am aware of light issues and shadows. I have learned how to fix noise and other technical problems and I try to take images that are technically correct to begin with so they don't need darkroom cleanup.
Others things I am doing:
1. Building a small studio in my home
2. Learning Adobe Illustrator for drawing and vector imaging
3. Approaching models with online model sites who are building their portfolios
It's going to be a slow process in getting to 500 images. I am closing in on 100 and that will be a nice milestone when that is achieved.
For now, it's been fun getting the sales and success I've had for a portfolio my size. 10 sales/month makes it enjoyable; it has to be because the work involved isn't worth the money. However, when I get to 100 sales/month, it will all have been worth it.
Keep uploading, keep trying new things, and keep learning!