(One day) Hot girls and appealing characters

[VitorCardoso]

So, of course I would like to be able to just scribble something down on paper spontaneously without looking for any reference or anything.

Understanding is definitely the way to do that.
So I already studied the biggest muscle-groups and most basic anatomy.

It's not just about knowing anatomy; you need to be able to create a good sketch. This is your main problem here: you seem to focus too much on anatomy instead of conveying a good structure and gesture through your sketch





learn to control the pressure of the pencil to make light strokes and don't be afraid to make many lines on the paper, making a good sketch is not about making a precise line but rather finding the best line through the scribbles

What are the muscles that have to be shown explicitly and what is all the stuff that can be blended together and simplified?

At first focus on learning the landmarks of the human body

I mean I could do 1000 life drawings, but still not be able to make a good looking anime-ish girl, for example.

Anyone who already has a good level of drawing fundamentals can do it