oh and one last thing, maybe get mana regen glyphs and hp quints
i say this because you get frozen pretty late, so the hp will help early game, and the glyphs barely give any attack speed, why not get more mana regen for more harrassment?

oh and i love exhaust/ghost combo too, they can both be used offensively or defensively which is pretty BA

get the spell pen boots, most of the damage you'll do (madreds/sotd/barrage) will be magic. and guinsoo's can be a pretty effective item, the upgrade from the pickaxe and blasting wand alone for 400g is amazing, not including getting 8 stacks of it for attack speed and ability power to help your barrage. nashors doesnt seem like a bad choice either, depending on what youre having issues with. anddddddd, why not pick up the 15% spell pen after sorcery 4/4?