The items used here are fairly common on most blitz builds and for a reason, they work, I focus mainly on mana based items giving blitz 3 advantages to exploit:
1. A huge shield from passive increasing his survivability and escape ability.
2. Dmg thru manamune and huge mana pool
3. Never run out of mana allowing you to perma run overdrive and spam grabs/punches.
4. The surprise factor of a nearly dead blitz having 2k health in shield to counter attack/tower dive.

Most blitz players avoid getting more than 1 or 2 of the mana items but I say grab them all!
This setup is effective and very fun to play, It will be tanky and pack good dmg, often getting fed and steamrolling, even carrying team or recovering from a bad start.

Key points of this setup: You have lots of mana and maxed cooldown, what does this do for blitz?
You can punch every 3 seconds giving double your attack dmg + sheen bonus = huge hits, you can often assasinate any squishy very quickly and leaving no chance of escape due to blitz abilities.
Overdrive is constantly on, you dont have to worry about mana and maxed cooldown makes it recharge right when it ends, you are permanently hasted both attack speed and movement speed.
You can grab more often and not run out of mana in middle of a teamfight plus your ultimate will recharge faster allowing more uses sometimes even twice in same fight if you open with it.

With this setup you are a ganker, a support and oftank.
you can suport your team pulling and punching into the air, interrupting with both your punch and silence or grabing any champions running away from teamfight making you invaluable in teamfights or as a laning partner.
By yourself you can kill most champions in 1on1 with a bit of practice.

Ganking: Run into enemy with overdrive and punch him into air, followed by silence to stop him from fleeing, 2x auto attack followed by another punch, if he still lives or tries to escape grab him back to you and punch him again, you will realize its very easy to grab a fleeing enemy as they tend to run in a straight line for their towers increasing your chance of grabbing if you wait for the right moment instead of initiating with it, can also counter flash or ghost granting you the kill.

Teamfight: Use grab to initiate followed by punch and silence from ultimate, let the rest of the team finish him while you go punch someone else, you have 3 interrupts!!! so make sure to nulify the enemy biggest threats, no other champ has 3 interrupts so blitz can be incredibly useful if well played, often you will punch that katarina ultimating in middle of your team, grab that olaf trying to kill your caster and silence their malzahar all in one fight making it an easy win for your team.

Survivability: Manacrank has great dmg but also great survival, you can easily run away with you superior run speed, punch and silence enemies trying to chase you and your shield will buy you the time and health you need to reach safety, as a rule always play hit and run, go in punch/silence/grab and run out, go back in do your combo and back out, keep doing this, and spreading your terror into several targets, together with another stuner or tanky dps makes incredibly laning power able to harass annoy and kill most enemy combos.

Use your speed to your advantage, pop into other lanes to throw a punch or two and run back to your spot, or go take blue/red buff while your item setup isn't complete, you have incredible mobility, use it!
Your ultimate is used mainly for silence and finishing enemies while ganking, when fighting 1v1 try to save it because 2 or more lightning arcs will be more dps than blowing the ultimate right away, use the active only for finishing or preventing enemies from fleeing (like kassadin for example). In teamfights use it to silence dangerous ultimates and try to get as much enemies in it as possible, since it recharges fast you might even get a second use if the fights lasts for 20+ seconds, if there isnt any imminent threat let the passive boost your dps.

If you read the previous sections you now realize better my choices:

Masteries: this are fairly obvious, the standart caster setup grabbing mana regen to help the early game, dont underestimate the 15% penetration for ultimate helping ganks and finishing, but you can also spend the 9 extra points into defensive tree for extra armor/mr and 3 points into strenght of spirit for hp/5 regeneration wich will be decent thanks to the large mana pool (40 hp/5 @ lvl 18 with full item setup). More importantly movement speed and cooldown plus your summoner spell improvement, this setup allows to reach maximum cooldown on all abilities and make the constant overdrive possible.

Summoner spells: Here I go with exhaust and flash, I feel they are the most versatile in manaCrank, they can be used to gank or to escape, ghost could be useful but you allready have overdrive, flash makes you immortal together with your huge shield or allows that last hit or grab on fleeing champs, exhaust keeps the super carries in check (trynda/yi,etc..) allows even better escape and can also be used to stop enemy from fleeing.

I might consider teleport for the early game wich can be hard without a good pair in lane phase or if your soloing.
Ghost for the crazy speed youll run out from bushes and spread terror on enemies, but more importantly for the collision ignore wich so often impairs our punches from landing on their gut.


Runes: Marks are obviously armor penetration.
Quints also penetration to add more deadly purpose against armor runed enemies and tanky opponents, Health quints can be considered for new crank players.
Glyphs are cooldown, together with masteries and 1 cd item will give you the 40% we so much need.
Seals can be changed to your choice of survivability: health per level, armor or dodge would be my best advice, my favorites are armor since you have a huge pool of extra health from shield wich is affected by armor.

Changing you item order changes your role and allows you to cater to your team needs:
Tear to start building up, you will rely on your mana shield for survival on early game so this becomes viable even without health or resistances.
Glacial shroud is key to the build, gives you the cooldown to perma run overdrive together with armor and mana for your barrier, this is a must but not your first item to grab usually third, second if against heavy AD. Get the shroud as third item most of the times, only finish frozen heart if enemy ad heavy or ad carry fed.
Mercury threads are much needed since all that health power and speed is useless if your slowed or stunned, plus we need the mr badly. Usually you second item.
Catalyst can be acquired early, this is great during laning phase for staying power plus grants the most survivability of all, but usually only after our core of CD and Dmg.
Sheen and manamune are you offensive options, Sheen will give a nice boost to your punches and with 40% cooldown it fits your 3 second punch perfectly, you dont even need to bother timing skills it will always land with punch. Manamume will grant you great dmg ( 90+ @ lvl 18 with full items) due to the huge mana pool and add more survival to your mana shield, your punch deals double your attack damage + sheen every 3 seconds, this from 2 items only will give 400+ dmg at mid late game, its all the offense you'll ever need.
Get at least 1 of the dmg items early, tear first into manamune is usually the best specially on higher elos, on low elos or pub stomp sheen start is very viable also.
Catalyst is upgraded to banshees of course for that extra survival, much needed mr and nice shield, and sheen into trinity for long games, the improved special and movement will be very welcome plus slowing enemies for ganks and attack speed to help farm.

This 5 items is all you need, change the order adapting to the game, banshee's first for magic heavy teams, frozen heart for ad teams, and mix the offensive items in between, all the items synergize heavily with blitz most giving both offense and defense plus they coem in small and average priced increments making manaCrank one of the best synergies i've seen in all champions, everything fits perfectly.

Lastly the 6th item can be switched as needed, guardian angel in most cases, in some rare ocasions more armor or mr for stacked enemies or even more rarely extra offense if your heavily fed and carrying the game: Black Cleaver or Last whisper fit perfectly in this situation but before adding a sixth item upgrade the entire core to its final forms, games rarely last long enough to see trinity force done, even less to get a sixth item.

Play around with different order, this items are all you need for every game but the order can change drastically. As a rule I follow:

1- Offensive item = Sheen or Tear
2- Basic boots
3- Finish Manamune and/or boots
4- catalyst or glacial shroud
5- glacial shroud or catalyst, grab the other one so you get both.
6- upgrade catalyst to banshees if having trouble with magic or shroud to frozen heart for AD, if your fed and dont need extra survival starting building the rest of trinity force, hammer for chasing, zeal for movement and better farm.
7- upgrade all the items to their final forms.
8- grab last item as needed : Guardian angel, Black cleaver, last whisper, any other mana or tank item.

This is a very fun setup after you get used to it and also very competitive, it is very versatile allowing you to oftank, harrasss/disrupt the enemy, initiate, gank and support as you see fit, filling any role your team needs.
You switch amongst the roles by merely changing item order and adapting to every enemy setup.
No champion or setup feels so right and synergizes so well as blitz, thats also why most guides dont vary much for him, this items work, its all about fine tuning and adapting to your playstyle.

Have fun and go rock the house with Manacrank!