Pros:

Your QER combo makes a champ useless for nearly5 seconds.
Area damage and silence with ult
Im a golem

Cons

Movement speed till late game
Mana issues early if hard harrasing

I choose to max first Power fist to reduce its CD and be able to farm easily early game, aslo Rocket Grab wastes a lot of mana and while being solo top you wont use it untill your jungler comes to do he´s/her work.

My runes are classic tank runes and solo top quintas which would let you last in lane longer.

I start with the mana cristal which will let me free farm till i get my catalyst the protector. When y get to the gold for catalyst and boots i generally recall, like lvl 5 or 6. Feel free to spam your ult to farm, it has a really short CD and your catalyst will make you regain the mana youloose for it. Warmog its next thing on my list, due to having a nice early defense with runes i focus on getting health. The important part next is to decide if you are going for the frozen hearth or the banshee´s first, depends on what the match demands. This build will really get high when you reach your atma impaler and trinity force.
Instead of trinity if your going really tanky you may want some MR so Force of nature is a great option. Or sunfire cape if heavy AD.

I pick Teleport and Flash but also having ghost instead of flash would work great combined with your W. Teleport could be replaced with exhaust that combined with ult makes a champ useless during the combo. Although, teleport is always usefull so you dont loose level.

Blitzcrank is the only champ that can make his enemies come to him, his grab is almost 1 kill if having an smart team and allows you not to engange too soon if you are losing or underfarmed. Your team just has to wait till you grab them and 1 enemie less ;).

Its my first moba build so i hope you enjoy it, ill be changin it while i get some things i consider should get in, enjoy the steam golem.