Disclaimer

This is just the way I build him, if you have a comment leave one, of course you can always tweak the build. You can always switch out Ignite with Clarity . You can also switch out Greater Mark of Alacrity for Greater Mark of Focus for cool down reduction or for more magic penetration switch em out for Greater Mark of Insight .

Start

First start with a Sapphire Crystal and one or two Health Potions .

Lane until you have enough to get a Tear of the Goddess and Boots of Speed .

After you have the Tear of the Goddess you should have enough mana to keep laning for a long while so now keep laning until you have the Giant's Belt , you have to have this, especially if you're the tank.

After you get the Giant's Belt

Get Ionian Boots of Lucidity

After you get that you should have a good amount of health and mana and should last a long time in fights, don't spam your high mana skills.

Now you can have a choice, if you think you can kill the other team then get a Stinger and build that into a Nashor's Tooth Blitzcrank benefits a lot from the attack speed and the cool down, if you're running out of mana fast (which you shouldn't be) then get the Manamune damage and mana = beastly!

If you get the Manamune then get the Nashor's Tooth after wards and vice versa.

Now get a Ruby Crystal and save 1.4k gold and finish with Warmog's Armor .

Now you have; attack speed , health , mana and damage.
If your team is doing well and you wanna get more aggressive get a Pickaxe and build it into a Bilgewater Cutlass

Now get a Hextech Revolver and finish with the Hextech Gunblade . Another good thing for Blitzcrank because it adds; AP , attack damage and life steal.

Now this is were your second and last choice comes in, if you're getting more assists then kills and you're surviving then go with a Mejai's Soulstealer

If you're facing mostly casters you can either go with a Banshee's Veil or maybe consider a Force of Nature both great additions with Blitzcrank.

If you're feeling ballsy and think you can do more damage in team fights then get a Needlessly Large Rod and make a Rabadon's Deathcap , or for more magic penetration get a Void Staff .

End

The way you wanna play Blitzcrank is the following.

Early Game

Early game Blitzcrank doesn't have much to fight,ideally you want to lane with someone who can stun of slow so when you hit a grab you can both get em. If you want to ensure the first kill or a kill in general sit by your turret and let the enemies get close then pull em in use your "E" skill and then ult if you have it, your turret will attack them while they're slowed and you will more than likely get the kill. Blitzcrank is slow so play safe and make sure your team calls MIA, because early, Blitzcrank isn't a tank yet so he can be ganked easily.

Mid Game

At mid game you should already have the Manamune and the Nashor's Tooth and the Giant's Belt and now building up for or already have a Warmog's Armor

Once you get to this point in team fights, aim your grab at the most squishy person on the other team and initiate the fight by killing the most squishy, another thing you can do is, if your teammates are all in one bush wait for someone to get close and grab them into your team and you all can jump em.

End Game

At this point the game should be over or close to being over. Now with your Hextech Gunblade and which ever of the five items you chose for your last item, keep on ganking, if by the end of this build the game is still not over then you have to do the bush grab or gank grab and then PUSH!!! End the game.