Hi there!! Peanut here..!
What I find helpful for my gestures is that I do it in three levels
Movement of the body (dynamism) > Proportions > Volume
Whether I finish with only the movement of the body + some small proportions or just dynamism only in the allotted time, I move on. The lesson here is to be expert in basics and be confident in your observation skills, especially in the proportion. Adding volumes (for me) is just icing in the cake, it is needed but not too important in gesture drawing.
Also, as a beginner you should allot more time, like 60 secs for dynamism + proportion and 2 min when adding volume. Speed is just the result of accumulating enough experience with anatomy and observation skills. Also, as I have said, developing your observation here is important so you can also limit your study for a few pose (5 images per day maybe..?)
Hope this helps