Right now I've done like 5 custom games with him, testing different runes, masteries and item builds. I understand that I still need to try him in real matches and that I still need more matches to get used to playing with/against different team comps. but what I've found has worked best is giving him offensive masteries (don't take sorcery, instead put points into Archmage's savvy and fill up crit chance, ability power, attack speed, armor pen, AD, attack damage, and Havoc). I put one point into cripple for exhaust. I gave him crit chance, magic resist per level, mana regen/5 per level, and your choice of some sort of defense rune for masteries. I build him so that his physical damage is increased. I think that the two most important items for him are hextech gunblade and spirit visage, and then going into lich bane for a big boost of damage. I'm still not sure which boots would go best for him. I build him like a hybrid (sort of) with some emphasis on attack damage and either armor or magic resist depending on what you're facing. I use ghost and exhaust.