I have been thinking about this exact topic for a while now. I think it really depends on what you’re going to be using them for. Since the lead/graphite is thin for a 0.3mm mechanical pencil, it may be a good idea to do all your fine/slow detail work with this. If you are going to draw quick sketches or gesture drawings with your pencil, then I would go with a thicker lead/graphite. Probably a hard lead as well since this will produce a light line. So, maybe a 0.9mm or a 2mm lead holder would be good for quick vigorous drawings… although, the 2mm lead holder is going to require a lead sharpener, which can be a pain to carry around if you’re on the go.
As far as lead/graphite goes, your local art store probably carries 2B (soft/darker line), HB (medium/semi dark), H (Hard/Lighter line), 2H (Hardest/Very light line).
Don’t get me wrong, there is a much larger scale of lead/graphite variants then this, but it is what my local art store carries, so that is what I gave as an example.
Again, same applies. 2B for high contrast darker lines, 2H for softer, lighter lines.
As I stated previously, I really think it depends on what you plan on drawing the majority of the time with that specific pencil.
Hope this was helpful.
Every child is an artist. The problem is how to remain an artist once we grow up.
- Pablo Picasso