Not Updated For Current Season
This a very different build to try, and if your not good at blitz, this probably won't be the one for you. However, if done right, this is also a EXTREMELY fun build to play around with.
Runes are just ones I'd go with, most of your damage is gonna be coming from your power fist and melee attacks. tho you'll still do a decent amount with your ulti, and rocketgrab.
Boots are kinda up to what you prefer.
Ones I'd go with would be:
Boots of Mobility - for 5v5s to get around or if you just like to stack movement speed.
Swift Boots - More reliable and all around good.
Ninja Tabi - If you like to stack dodge like me and get the run speed boost.
Berserker Greaves - Get an extra bonus on Blitz's attack speed.
The rest of the build is basically about multipliers.
Sheen will double the damage of your next attack, with powerfist you can triple the damage of said spell. This is Great for knocking out towers, as at max rank, you can do this ever 3-4 seconds with some cooldown reduction.
From this you get double zeals to give you more run speed, and more importantly give you a decent amount of crit for a low price. Next go ahead and finish Trinity Force since it's a little bit cheaper, and will help you all around with more AP, health, Mana, etc.
AFter that, Finish off Phantom dancer to get even more dodge, which will help with your survivability against melee classes, more crit to keep up the 400 percent punches from powerfist, and again, even more movement speed.
What are you gonna do with all this movement speed? Well when it's stacked up this high, with your pop up and rocket grab, you'll be able to continually mash on opponents while they're trying to run away.
Which is why I recommend Frozen Mallet to make that even easier, and give you a decent amount of health as well to tank towers with late game.