First of all: those drawings look amazing, your style is certainly interesting. Take this critique with a mountain of salt because I am not as good as you.
Second: What are you trying to improve? Anatomy? Gesture? Expressions? Shading? Without a precise pointer is hard to give you tips.
Your chaotic lines are good for everything above the 30s. The 30s look too much chaotic, wobbly and amateur. I want to clarify, I am not critiquing your style, there is a difference between soft skills (free drawings, do what you want) and hard skills (perspective, technical drawings, gesture). When you hard ones reduce the stylish element, don't eliminate it completely, simply reduce it. If you want to know more about soft and hard skills I recommend you read The Little Book of Talent.
Third: I want to see your finished drawings. The red effect on paper is absolutely amazing.
Keep practising and improving and you will become great in no time.
PS: Which Brush makers did you use? I want to try them.
I haven't really been practicing with a goal in mind, so I think setting one will help (probably anatomy, and creating dynamic poses)
For those 30s ones I hadn't been sketching out the line of action, nor the sorta basics of the body, but I think that may also help.
And I use the Sakura Micron Brush pens in red, blue, and black
You have a very good start going, and I very much like your use of the brush pen. One thing that will help you a lot is to start constructing your figures more. You seem to have a good knack for visually seeing something and copying it down by contour. To solidify this linework you could start thinking about it more as form instead of line. Like you could draw the armature of the pose, the general blocky shapes of the limbs to get the spacing right-- and then going back over and deepen the lines that you want and start to draw in the specific feature. If you're using brush pens like you are, that black line over red guy is a perfect example of this.
Like the red line could be your 3d construction of the forms of the body, and the black line your final 2d line drawing over it.
Your drawings look great! I like the use of the brush marker, give the drawing personality! I may suggest to focus more on drawing the line of action first, then pencil down the shapes of body, and finally refine them to the level your are now! It should helpful with capturing the dynamic of the pose! Looks awesome, fantastic work!