First, a few short words on how to properly use and read this guide:

I, dear reader, am writing this guide on behalf of Master Tier* and world renowned Blitzcrank player, Spectacle. Think of me as merely a conduit of the wisdom that Spectacle is about to impart to us all. Friend if you're anything like me, you've quickly realized that Blitzcrank is the one champion in League of Legends that can single-handedly carry even the most bronze-laden team back from the clutches of defeat, straight into the jaws of victory as the phrase goes. Please join me on this epic journey of self-discovery and learn from the master Blitzcrank player Spectacle himself, how to unlock your inner Blitzcrank. - Elwin

*NOTE while Spectacle is Master Tier on the OCE and LAN servers, he is still only Gold 4 on NA. Go figure.

Hello friends, Spectacle here. It's important to get your runes and masteries directly from ME, Spectacle, as even the smallest deviation from this guide will probably, (when I say probably, I mean DEFINITELY) result in catastrophic failure akin to one of HotshotGG's various haircuts. That said, the most optimal way to plan your masteries for maximum Blitzcrank potential is 0/0/30 as seen below. There's literally no reason to take any points in the offensive or defensive mastery trees as Blitzcrank is inherantly offensive and defensive as a champion. You can only hope to augment his usability by fully speccing into the utility mastery tree.
STEP 1: Use only Tier 1 runes. I REPEAT: use ONLY Tier 1 runes. Tier 3 runes may appear at first glance to be attractive due to what I call, "stat inflation". Do not be deceived; Tier 1 runes are inherently better than Tier 3 runes. Why? Simple. Do you want to be number 3, or number 1?

Blitzcrank scales best off of mana runes due to the fact his passive Mana Barrier is greatly enhanced the more mana you gain. You want to also run movement speed quintessences as they enable you to get back into lane faster.

Step 2: The only two viable summoner spells on Blitzcrank are Flash and Ghost as they are dual purpose in the sense that they allow you to either catch up to your enemy, or get back into lane faster. Many summoners overlook the fact that Ghost shaves a solid 5 seconds off your return trip to lane from the base platform.

You want to start out with a Sapphire Crystal and two Health Potions. Your goal is to get a Tear of the Goddess ASAP. There should be NO REASON to start with ANY other items. You also want to get a Sightstone on your second or third back as this will enable you to keep a continuous stream of wards on the map so nobody can blame you for not doing your job as a "support" champion.

I'd also like to point out that unfortunately, I've found that most people will not be receptive to the idea of being carried by Blitzcrank. Your best bet is to quickly dispel any notion that you're in the game to facilitate your teammate's success by using your ultimate Static Field to clear minion waves. They'll quickly get the picture.

If you end up with >= 1600 gold when you back, you buy a Needlessly Large Rod. I don't care what you need, you get that damn rod. If you have >= 3200 gold, you get 2 rods, etc...

Finalize your build by grabbing Mobility Boots with the Homeguard enchant, Mejai's Soulstealer, Archangel's Staff, Rabadon's Deathcap, and Void Staff. The combo of infinite mana from Archangel's Staff and unmatched damage from Rabadon's Deathcap and Mejai's Soulstealer will let friend and foe alike know that it's business time.

As proof this build works, check out this snapshot I took of my match history. What more proof could you possibly need?