Would it be advisable to learn cinematography by starting out with, in my case, a Canon e-400 SRL camera? I want to learn about the technical details of photography like lighting, aperture, shutter speed, lenses, etc, before I try renting a 16mm camera and making films.
I don't have a lot of money right now, nor do I have actors or a script to try blocking scenes with. Would I get any benefit from learning to take still shots before moving up to motion photography?
Quick answer: yes! You can learn a lot from taking stills, a lot about composition, about lighting, about using natural light. You can shoot series of stills to make a photo storyboard.
If possible, work with a light meter. (You say you are going to eventually shoot film, not video.) Figure out the relative ASA of your digital still camera. Or, even better (but much more expensive) shoot film. In fact, shoot slides, since the margin for error is much smaller than with negative.
I Think that a Base knowledge in photography is essential to cinematography. It sounds a little extreme but go buy Ansel Adams book "the Camera" It will explain photography in ways that can be directly used in cinematography. I think it's the single best photography book for anyone wanting to learn the core use of film principals.