In my internet wanderings, there doesn't appear to be much in-depth material covering this topic. I often wondered how I was supposed to do it, what camera I should use, or why I should be doing it in the first place. The following article lists three reasons why gathering your own reference is so important.
1. The Reference is Yours
This point is especially targeted towards young artists. In my opinion, I don't want to be paying extra on something if I don't have to. You don't need to be wasting time searching the internet for a creative-commons-proof-photo or purchasing rights to another person's photography. Whatever you capture on your camera is completely your own, giving you the freedom to use it however you wish.
2. Limitless Possibilities
The angles, the lighting, the model - the possibilities are endless! The internet is full of information and resources, however, it's only a two dimensional tool in your three dimensional world. When you reference an image from the internet, you can only see one angle of that image as well as its lighting, making your resource severely limited. When you shoot your own reference, however, you have the opportunity to walk around the model and see the potential composition of your image at every angle. You can also move the light wherever you want. It could be that an idea for the model's pose and lighting becomes overshadowed by an even better pose and lighting you discover during the photo session.
Let's say you want to reference an image off the internet, but you want to tweak the pose or the lighting a bit. Without ample experience drawing from real life, you're simply guessing at how it should look. This guesswork runs the big risk of creating something that isn't believable. Observing things like clothing folds, the reflected light on a sword prop, or the weight of a figure in space fills the gaps in your knowledge. Because you're pulling information directly from your reference, your work will have a higher degree of accuracy and credibility.
Side note: This advice is meant more for the beginner than for the master. Over time, a master has referenced so much from life that he or she has the ability of creating something convincing, even if there isn't an exact replica of the subject in front of them. Consider Donato Giancola's work, especially with his androids. There isn't an exact android model sitting in front of him as he paints. Instead, he combines live model reference with his understanding of metal rendering and anatomy. What results is beautiful, convincing, and believable.
Call to Action
1. Read up on artists who gather their own photo reference. Donato Giancola, Greg Manchess and Dan Dos Santos are good examples. Some have different methods than others, but all agree the practice is important for their work.
2. Draw from life. It doesn't have to be just your photos. In fact, drawing from life is ideal!
You're doing better than you think. Keep going!