Oh wow, what a question, it all comes down to the good old practice, I've been doing gesture since 2020? I wanna say end of 2020 but I'm not so sure, anyways, a long time, and I absolutely sucked at it and, believe it or not, I still think I suck at it, but waaay less than when I started at it, I will try to answer your question in the best way I could manage, but basically when I'm doing gesture I try to focus mainly in the three main masses and the weight/balance of the body, I start by drawing the head and try to show where's it looking at using a cross, then drawn the line of action starting from the bottom of the neck all the way down to the croch or upper part of the butt, I try to really exaggerate the curve of that line, then I look for witch leg is holding the weight of the body, I usually do one stroke to represent it, then the other leg and so on, arms usually don't matter that much, if I have time I try to drawn the landmarks of the body, especially the bottom part of ribcage and try to indicate any foreshortening by using ellipses, I find out that after you start to learn the very beginning of anatomy it seems like everything just clicks, of anatomy, I only know about bones and pecs, but only that inicial knowledge helped me so much in doing gesture, oh and I remember doing proko's free version of the figure drawing course in his website, that helped me soo much that is unreal, about the line economy thing, I have a book from Andrew Loomis, figure drawn for all it's worth it, in there, there's a simplified version of a figure manekin, I inspire my gestures heavily on that manekin, hope this helps.
