Intros are for english essays. Lets get straight to it. Blitzcrank's Rocket Grab and Ultimate are heavily dependent on Ability Power, and his other two abilities, Overdrive which increases attack speed and critical strike chance, and Power Fist which deals double physical damage. So it is crucial to focus on both of these while considering your build. Blitzcrank, when built properly, is a one-hit wonder when using all abilities simultaneously. Once an enemy is grabbed, immediate use of Power Fist, Static Field, and Overdrive, in that order, will most assuredly cause devastation for an enemy. Try to avoid speedy ranged characters, and be sure to approach as stealthily as possible for maximum likelihood of landing Rocket Grab. Effective use of Rocket Grab can make or break your gameplay.

Again, maxing out ability power not only increases damage done passively by Static Field, but also Rocket Grab and Active Static Field. Therefore increasing both AD and AP is crucial in all aspects of developing this character.

Everything about Blitzcrank depends heavily on AP and AD, which is the focus of the Masteries.

I cannot stress enough how important it is to build with a strong Ability Power base. The Rabadon's Deathcap was made for Blitzcrank, as his two strongest attacks are effectively doubled with a good AP build. Because of this cost, however, farming is very important, and is discussed further in detail. Build starting with ability power, alternating with attack damage to make sure your Power Fist is equally as damaging in conjunction with Rocket Grab. Using these two together will get you early-game kills with a strong early build. All of these items capitalize on Blitz's abilities; starting ability power for Rocket Grab to help boost early-game damage, Berserkers Greaves for attack speed stacked with Overdrive, Blasting Wand and Rabadon's Deathcap for godly ability power, and Black Cleaver for major AD and more attack speed. Everything falls into place. The reason why there is no need for armor or magic resist is due to his passive ability, Mana Barrier, which will give you a shield should you need it, but once enemies get a sight of how much damage you do if they get close, you should have no problem with people taunting you. Remember, a good play on Rocket Grab can save you.

Everything in Blitzcrank depends on your ability to use Rocket Grab. Luring enemies close to your turret and using this properly can almost triple your damage, especially with the stun effect in Power Fist. Developing Rocket Grab and Static Field is the main focus, as upgrading Power Fist merely reduces cooldown time, and upgrading Overdrive increases attack speed and crit chance, but not by much. Upgrade priority follows this order, from highest to lowest: Static Field, Rocket Grab, Power Fist, Overdrive. It is because of this cooldown reduction of Power Fist that upgrading is crucial, because double damage more often is SICK.

I'd personally recommend Exhaust and Flash, because Flash is just always useful for running away or chasing, and Exhaust is particularly effective with Blitz after use of Rocket Grab, to keep them from running after you pull them towards you. If I want to go for the kills, I might pick Ignite, a deadly combination with Blitz's stun with Power Fist and crazy damage with Static Field. Ignite can be used to get that last little bit after going ham and QWER'ing your enemy, if they're not already dead.

AP, AD.
AP, AD.
AP
AND
AD.
Usefulness of Rocket Grab cannot be underestimated. It has a steep learning curve of placement, but once you can master that, the game is yours. I will explain a few tips below

Ok heres some tips for mastering Rocket Grab:
a) try using it to check if grass is clear
b) aim where you anticipate them to go
c) DO NOT, i repeat, DO NOT use on enemy running away. Blitz stops for a split second before shooting the grab, and this is just enough time for the enemy to get out of your range if they're not close.
d) Rocket Grab has a lengthy cooldown time, so effective targeting is key. If you miss, you're going to have to chase the enemy down, which is not such a good strategy against ranged champions.
Basically, Rocket Grab makes Blitzcrank unstoppable, but poor usage just makes him a walking target.

Because of the expense of some of the later-game items, particularly BF sword and Needlessly Large Rod, farming is crucial to a good Blitzcrank game. This is made relatively easy, though, with the help of Static Field and a high AP. Ideally, when both the enemy champion and enemy minions are in your midst, use of Static Field can not only land high damage to enemy champions, but also wipe out entire waves of minions in one hit. Keep an eye out for late-game empty lanes, and take advantage of them.