Before I go into anything. I want to talk to you about the combo. Due to the way the masteries are set up now, it takes a bit of work. If you can't land skillshots, don't try this or it is really hard. You want to W to catch someone really quickly, then you pull them towards you with your Q, while they are Stunned (be careful, because the stun only lasts for approximately .5 seconds at max leveled Q) you need to immediately E them, if they are still alive, just ult and run. Because by this time, the rest of the team is probably colliding.

I'm actually a Challenger-level smurf, and I have been playing Blitzcrank jungle for as long as I can remember. To be honest, the reason I am making this guide is because my friend that wanted me to teach him how to Crank in the jungle. He encouraged me to share my ideas. So here I am.

Just read the notes for boots but I have a ton of viable other builds that I've run with Blitzcrank.

Devourer Blitzcrank:
Challenger's Sabre: Devourer
Boots of Mobilitiy/Ionian Boots of Lucidity
Infinity Edge
Essence Reaver/Bloodthirster
Statik Shiv
Phantom Dancer

That is a Crit Crank build. You just walk up, smite someone, then use your E and one hit someone while procing your Devourer on your E, which ends up TRIPLING the damage instead of doubling.

Phantom Dancer and Statik Shiv are also viable on Warrior Crank.

Always max your Q first, it lowers the cooldown, increases the damage, and increases the stun. Your E doesn't increase any damage or anything else, it just lowers the cooldown and increases the mana cost. It's really not worth maxing it until last. Always level up your W second, it increases mana cost, increases movement speed, lowers slow duration, lowers cooldown. Such a good ability for any AD Assassin. Always level up your ult when you can, it silence enemies, does damage, and has a ridiculously low cooldown.

Depending on who their jungler is, and where they start, I get a hard leash at Red OR Blue buff, whichever is directly opposite from where your opponent started. At level 1 you start your Q, and level 2 you start your E. Do not smite the buff you take first. At this time you should go to your opponents buff and ward it. Wait until they start it. When it starts to get low, Q it through the wall, E it, and then Smite it if it didn't die from your Q and E. Then just continue to jungle. It's easier from there on.