Nice build but your item choices could use some improvements, First lets start with manamune, manamune is an overall useless item on blitzcrank and there should be no reason you need over 2500 mana on a blitzcrank ever. Second, i find Ionians boots of lucidity to be ineffective and instead I think you should counter any kind of ganks on you that would ruin your jungle by getting boots of swiftness. Getting boots of swiftness with your "W" you will be able to out run early game yi's ult and outrun a charging volibear with ease. (To counter any fast running champions). I find a hextech gunblade to a bad choice of items because instead you could pick up a rod of ages mid game. And as for frozen heart, I do not think this should be built, if I were you i would get a zhonyas hourglass for the bit of armor it gives and the 110 AP aswell. Overall I believe that you should rush build cloth armor 5 health potions beginning of the game, you should then rush a catalyst of the protector and get your boots of swiftness, You should probably then build a phage, sheen, and then rush a trinity force, aftwerwards I suggest you buy banshee's veil, Then build a heart of gold, a wardens mail and a catalyst of the protector, you then get a randuins omen, a rod of ages, and finish build with a zhonyas hourglass. (I also think you should dedicate more of your masteries into defence and the remained into expanded mind and some AP masteries :) you should also change your runes around a bit so that they are better geared for AP. I hope that you take some of my advice into consideration :D

(Holy **** i typed alot xD)