The effect of this build is that Nocturne does crit, got good movement speed and does enough damage and still a lil tanky. taking some little cd reduction for the ult.

i made my choice by only picking 9 points in the damage masteries, 21 for the "tank" masteries i did this for jungler cause it makes it way easyer got more health dealing more damage and get less damage from creeps.

Marks: i took armor penetration runes for some good penetration u could also take attack damage runes for that. but the effect of penetration would give u some more dmg advantage.
Seals: i put armor runes there for taking less damage on champions and minions.
Glyphs: u got 2 choices Magic resist or Attackspeed. Why attack speed? i like it with this build cause u got good movementspeed u can always hit him, with an big attackspeed u will kill fast or regen fast from life steal.
Quintessences: I picked Damage runes cause they give a good and big bonus u need the damage cause if u pick penetration on the mark runes u got no damage