I'd suggest getting a couple of books on drawing. For instance, comic strip artist Byrne Hogarth came up with a series that includes Drawing Dynamic Hands, which gives you some good pointers on how to construct the human hand, which forms the basic framework for the guestures that you're learning to draw. It also helps to have a mirror handy, as your own hand can serve as a model.
Photos are okay to use if you don't have access to a live model. The whole point of gesture drawing is that the speed forces you to only focus on the anatomy of whatever you're drawing rather than the detail of the overall subject. Pose-maniacs is a pretty useful site,since it does just that plus the 3D technology gives it a more realistic approach. Although I do suggest taking a life drawing class in the future, the guidance of an instructor and being involved in an artistic environment can be helpful and motivational.
Gesture drawings are fine at any skill level. They're used mostly as a warm-up and/or to get a sense of the pose or gesture of the figure. You're supposed to work very quickly, no more than 5 minutes, getting a basic idea of the form down. In life-drawing classes, they're often done at the beginning of the session, with the model changing poses in quick succession. If your goal is to improve proportions, they're not really going to help you there. At most, they'll get you comfortable with drawing the figure and getting an overall sense of how it works.