For most graphite drawing purposes, a 2B and 6B graphite pencil on hand is all you will need. Graphite comes in various densities, however, and keeping a mix of soft and hard graphite can allow you to achieve different effects. The softer graphite is good for blending and harder graphite is lighter and used for drawing outlines. Some artists choose mechanical graphite pencils for more consistency in the balance of the pencil and the application of the graphite. Graphite pencils are available (from soft to hard) in 6B, 4B, 2B, HB, F, H, 2H, 4H and 6H.
You should not use your finger to blend graphite because the oil from your finger can be picked up and cause damage to your drawing. Stumps and tortillons are made specifically for blending graphite in drawings. Either can be used. They are typically double-ended and cylindrical and made of tightly rolled paper.
Progresso Pencils are solid sticks of graphite that can be used to cover larger areas than traditional drawing pencils. Progresso sticks are used for coloring large areas of a drawing and adding shadow and depth. They are frequently used for lightly adding color over a canvas before drawing begins.
A color shaper (used much like a tortillon, but with more precision), a standard pencil sharpener and gum eraser are essential tools for graphite drawing. Putty can also be used if needed, to lift graphite away from the paper.