ckarsanac, first of all, I want to command you for doing something at 40.
Secondly, 30 seconds figure sketches are more for capturing the movement more than being a full drawn figure. It will look stiff and horrid and you will want to erase it/throw it away, but i'd tell you not to.
If you want a good website to teach you from the start, I would suggest Draw a box or CTRL paint.
They are equally good to teach how to draw, in different ways.
The reason I am saying that is that yes, you can draw 100 figures and get a bit loose, but it may not ultimately give you all you need if for example you want to make a full blown illustration.
I would also recommend the Loomis books or the Scott Robertson books (which also have videos), figure drawing and head for loomis, matte painting videos from Scott Robertson.
It is mostly after you've gone through this that you can finally draw a full blown illustration. I won't tell you that doing gesture drawing is bad, but I will tell you to do it everyday. The more you draw, the better you are at it.
Stick to 30 seconds for 15 minutes if you can, then learn a bit more from the other links I gave you, do the exercises, and after a few days/weeks, you'll see something click.
You can then compare your old drawings to your new drawings and look how far you've gone :)
Never give up!