Lethal Tempo allows you to output a massive amount of damage on a gank after using [R]->[E], allowing you to get in a ton of auto attacks before the fear ends.
WhyPresence of Mind
Presence of Mind allows you to assassinate and blow up targets with [R] while massively resetting the cooldown after a successful kill for more map pressure.
WhyLegend: Alacrity
More Attack Speed means more damage output/synergy with Lethal Tempo as well as a faster jungle clear.
WhyCoup De Grace
Coup De Grace's execution play pattern synergizes well with Nocturne's want to execute squishy targets with [R] burst.
WhyCelerity
Celerity's bonus AD with movement speed paired well with both Waterwalking as well as Nocturne's [Q] for extra kill threat.
WhyWaterwalking
Waterwalking is fantastic on any jungler as it grants you a massive amount of early game jungle pressure.