Do you even need that many different pencils?
Are the different degrees of hardness for pencils complete nonsense or is it worth drawing with different ones? You can basically draw with any pencil, but if you only stick to one, the drawings will always lack something.
The degree of hardness always refers to the lead in the pencil and gives information about its mixing ratio of clay and the mineral graphite. Clay serves as a binder for graphite, which gives the pencil its black colour.
The mixing ratio is given in units ranging between H and B. The higher the number in front of B, the more graphite it will contain. The line becomes darker and the lead softer. The higher the number in front of H, the more clay it will contain. The line becomes lighter and the lead harder.
A 6B pencil would not be suitable for technical drawings because it cannot draw fine lines and is easily blurred. In the same way, a 4H is also not suitable for an expressive portrait drawing, because it is too bright.
One pencil alone will not be able to add depth to a drawing. No matter how well you work, without a wide spectrum of brightness and darkness, the result will always look flat.
This drawing was drawn only with an HB pencil. The hair could have been much more convincing if the strands had been drawn with softer pencils to get more darkness. The same applies to all shadows in this drawing.
Another problem is dark shadows: If you try to draw them with a hard pencil, it simply doesn't look convincing and most of the time you can see the strokes of the pencil.
In this drawing from 2011, some harsh strokes are intended, but in the lower jaw region, you can see it does not look good.
For sketches, I recommend a 2H pencil. All lines can easily be erased and it can be covered by any softer pencil. Other things that can be drawn well with a 2H pencil are skin and light areas with only light shadows like eyeballs.
I use the HB pencil especially for drawing medium shadows. These are, for example, in the crease of the eyelid, in the corners of the mouth or under the nose.
Depending on the darkness of the shadows, you can use all the soft pencils. In order to keep the transitions smooth, I recommend to yourself from the lighter to the darker pencils.
There are also the odd numbers available like the 3B, but to me, the differences are not that obvious so I usually skip these.
In this drawing of a friend with very dark hair, a 4B pencil was used for the hair as well as in the sunglasses to create a balance.
A long, long time ago I experimented with an 8B pencil and made this drawing. It has to be kept in a plastic wrap because the 8B is so soft it ends up everywhere: on fingers, clothes, neighbouring drawings and more.
There are many manufacturers of pencils, so you can quickly feel overwhelmed by the variety of products.
I personally prefer to use pencils from Faber Castell and Rembrandt. Both brands offer great quality in leads that do not suddenly scratch the paper while drawing and do not break immediately after a fall from the table.