A gesture drawing is like the artist warm up exercise. Just like athletes warm up before running or swimming, artist too should warm up with some quick gestures. A gesture is normally about a minute long, no more than 2 or 3 minutes. It's meant to capture the feel and motion of the subject model.
A dynamic (full of energy) gesture drawing always has at least one line of action. It's the energy flow of the drawing, and how you guide the viewers eyes through your drawing. It's something you keep in mind while drawing OR can draw the line before hand. What ever works best for you.
Here I did a 1 minute quick sketch of this sword dude. He was pointing to something off in the distance and my intention was to convey that. He's leaning his body forward and if you see, I aligned his shoulders and arms to form that action line. There's another action line going from his right foot to the tip of his hat, once again to channel his energy forward.
So try it next time you draw. It'll improve your drawing, composition, pose, and help you tell that story that you want to tell with your drawing.