Your item set is bad and you should feel bad.
Health Gem as a starting item is a poor choice because it leaves you no money for potions. Starting potions are handy because if you get hit hard at the beginning by the opposing team lurking in the bushes or etc, you don't have to go back right away. It also gives you more resiliency against harassment.
Leviathan is highly questionable. As a Tank/Initiator, you're often going to die and probably not frequently going to be getting the last hit on champs.
Tear of the Goddess? To what end? If you're really having mana problems, try something like Chalice (starting of Meki + 2 Pots into a Chalice is a good way to begin), which gives you all the mana you'd need plus some handy MR.
Malady is an item that's only really good on a few champions: Warwick, because he hits them in rapid succession, really stacking the damage, and Twitch, because he can spray and pray it over their entire team. For Blitz, you're MUCH better off going Bloodthirster or Stark's, Stark's helps your team (and has nearly as much Attack speed and 5% more lifesteal than Malady) significantly, while Bloodthirster increases your burst damage. And let's face it, your job is to Grab -> Power Fist -> Static Field for a burst damage kill, not to try and attack someone for several straight seconds in an attempt to DPS them down.
Last Whisper is a great item, but it is terrible with Black Cleaver, as the cleaver's reduction applies first, weakening the Whisper's Penetration.
If you really want to go high-damage Blitz, I would suggest starting off by building Sheen, then build it into Trinity Force. This will massively increase your Power Fist damage, as well as giving you all kinds of useful stats. After that, standard DPS fare (Infinity Edge, Last Whisper, Starks/Bloodthirster) round you out.