Gain 10% CDR when you reach level 10. Excess CDR becomes AP or AD, Adaptive.
Electrocute is Fiddlestick's most reliable form of gank damage and the extra burst allows you to kill your target before your [Q] fear wears off.
Sudden Impact empowers Fiddle's primary fight tool, his [R]. The blink on [R] will grant you a bit of extra Magic Pen for more gank damage.
Eyeball Collection's stacking AP allows you to snowball any small lead you get from ganks in to a huge lead.
Ultimate Hunter is fantastic for capitalizing on successful ganks and snowballing into more rampant ganks with Fiddle's fight-winning [R].
Nimbus Cloak synergizes perfectly with Fiddle's desire to burst into a team with a well-timed [R]. The extra Movement Speed from your passive as well as Nimbus allow you to quickly get to the backline.
Paired with your item build and Ultimate Hat, Transcendence keeps your [R] on a minimal cooldown in the mid-game so that you're able to threaten ganks far more regularly.