Gestures are difficult starting out because people that know how to figure draw can rough out gestures in seconds and they look good while you can spend 10 minutes trying to get a squiggly character to look non-retarded. I always found gestures a terrible way to start because the average person doesn't understand the basic proportions and anatomy of the body. Telling them to make exaggerated S and C curves for the spine and arms and finding the line of action and expanding on it and so on is confusing and they don't even know how to make the basic body yet.
Another factor is how you do your gestures and how little or much detail you want. How far towards a figure will you go? All lines and oval head? Chest, head and pelvis as solid objects and rest lines? Simple cylinder limbs? Everyone has their own gesture style and rough outs for thumbnails. Some have more detail and build into a rough figure made up of cylinders and other shapes and then come back over for detail in a 3 or 4 step process. Some just teach basic gestures. Some use Loomis style with the oval hips and ovals for joints with lines connecting. Which is right? Which should I do? Most try to copy a gesture already drawn instead of understanding the human body and the shape and form. Doesn't really matter what form of gestures you use as long as you capture the basic gesture. That's hard to teach and hard to see results from without a basic understanding of anatomy and the figure.
On where to learn it, it will either be personal lessons and drawing from life or a variety of resources from across the web. Proko isn't as bad as you say though. Their videos are built across dozens of videos and are meant to be samples of their full course. If you only click gestures, its going to be bad as they have pencil holding and line techniques in other videos and build on shapes and practice examples in earlier videos.
There are more clinical approaches to figure drawing that take draw a box style techniques of literally drawing boxes or perspective grids. Ex 1 - simple perspective grids for poses and proportions. Ex2 - same for foreshortening and perspective. Ex 3 - you can just put them in a box and expand on it if you understand proportions and the rotation of limbs and limitations of movement. Ex 4 - another foreshortening in perspective.
Gestures are, again, style based if you ask me. I prefer starting from the 2 main forms - chest and pelvis - and then adding the head based on their positioning. It looks almost like this. If I'm looking for specific poses, I might do something like this or this or just the 3 main forms like this.
Humans are extremely difficult to draw compared to just about anything else. Minor anatomy issues are amplified tenfold. It's easy to see it looks wrong, but many wont be able to tell you why it looks bad either. It's a long road to drawing believable looking humans. It's why drawabox is so good - you get results quick with animals and plants and vehicles. Anatomy and human forms will likely take more than the sum total of all time you've spent on drawing to date. Expecting instant results and perfect gestures from one video tutorial is asking too much. Fill an entire 50-100 page sketchbook with gestures. Fill pages of heads from every angle, arms bending, torso/pelvic combos bending and twisting adn so on. Once you have a basic understanding of various parts, then you can go to a site like http://reference.sketchdaily.net/en and cycle through poses every 5 mins and work your way down to 2 min and 30 sec poses. Taking images and tracing the basic shapes over top with tracing paper or digitally is another way to identify forms and build up muscle memory for the shapes.
It's a long journey to making competent looking gestures. Some start there, but I think basic construction of the body broken down into simple ellipses and cylinders and cubes is a better starting point. Developing your own style for gestures based on how you construct the basic shapes (ellipses for hips or the ribcage chest some do or just cubes for the chest and pelvis - up to you) is how I would learn or teach it. Relying on one video or tutorial wont cut it though. Expecting significant results copying their gestures wont cut it. Practice, practice, practice. It's probably why drawabox removed his previous figure lessons. It's far too complex a topic for a quick lesson or one or two videos.