Somehow it happened that the pen, ball or gel, is recognized only as a tool that you can write, but certainly not draw. The exception is unless scribbles in abstracts. However, I really want to refute the stereotype, because I know for sure: drawings with a gel pen, just like a ballpoint pen, can be real masterpieces. These tools are suitable for drawing no worse than the same pencils, pastels and other artistic materials.
Personally, when creating my drawings I do not use preliminary pencil sketches, since my hand is already full. However, it is better for novice artists to sketch out with a pencil what they would like to portray. After erasing the ink with an elastic band is not possible, and to create a drawing with a gel pen, you need a firm hand and confident movement. If the brush falters, it will not be easy to fix the drawn one. The complexity of drawing with gel ink is still that, with whatever force you press on the rod, the lines from under it will appear the same in saturation. You can only reduce the thickness of the lines, holding the handle under a slight slope. Therefore, creating really beautiful drawings with a gel pen, it is very important to pay attention to hatching when applying shadows and penumbraes. In the darkest places, the surface will have to be shaded, or, to put it more simply, paint over. And in order to smoothly move from a shaded area to a lighter one, it will be necessary to make strokes - more and more rare, coming to naught.
With a ballpoint pen in this regard a little easier. In this case, the saturation of the tone can be adjusted with the help of pressure: the stronger it is, the sharper and sharper the line. Almost the same noticeable movement of the rod along the paper gives pale, slightly prominent lines. And small defects can be carefully eliminated, using either a rough eraser, or a special clerical putty, better known as "Bar". True, the paper in this case should also be white, and the layer "Stroke" - thin and paint only what you need. When using a rough eraser, it is worth considering that the paper should be sufficiently dense. Inadmissible, correcting drawings with a black handle, rub too hard. You can just do a hole.
But whatever the pen you draw, note that this is not a pencil, which if necessary can be grinded to get some volume. Although, strictly speaking, rub it and it is not accepted. Drawings, in which traces of rubbing, are considered a mauveton and a sign of the artist's unprofessionalism. Therefore, when creating drawings with a gel pen (or ball-point pen), achieve a three-dimensional image only by hatching. And this is by no means even lines. If, by drawing a ball, you shade it as a ruler, even if you take into account the shadows and light, you will get a flat circle. To achieve dimensionality, the direction of the strokes should not be thoughtless, but as if repeating the contours of the ball. The same goes for other subjects. Therefore, before creating the drawings with a gel pen or a ball pen, practice shading with a pencil: work out all the directions and types of monochrome filling, pressing, gradation, uniformity, etc. After all, the shading must support the shape of the object, and not distort, if they are not required by those or Other individual elements of the figure.