His early clears are slow, and good only in the sense that he can be at full health through it all.
This season, I've been starting with a red buff clear, backing for an upgrade into Trailblazer, continuing with a blue buff clear, and then ganking with double-buffs or taking more camps. I'd hit 6 faster this way, often ahead of the opposing jungler.
Being able to upgrade Trailblazer with Magus was a nice power spike before working on Zhonya's, and gave even faster clears. I've never liked rushing Zhonya's because Armguard doesn't give a power spike, and Rod takes a long time to buy. You also don't need the active until 5v5s in the second half of the game.
The upgrade with Runeglaive does little for Fiddle. By the time you do so, he's able to chain Drain and Darkwind. This change screws Fiddle, and it's because he's an outlier that simply doesn't want to auto-attack.
I'm not quite sure what I'll do with jungle Fiddle now. I probably won't upgrade Trailblazer anymore, and get a Blasting Wand instead. Then work on Zhonya's followed by a faster Deathcap or Void Staff.