first of all ,you will take flash and ignite.flash will give you lot of range so you can use your ulty which has nice range too and ignite is generally good.you can also take exhaust and ghost if you prefer these spells.Your runes will make you more tanky(mr and armor)and 15 ability power plus your masteries and doran's blade to start get your full passive.For items start with doran's blade for your passive,second get your boot which will be mercury if they have strong cc or magic pen boots,it depends at the enemy team.Third is gunblade ,start with the spell wamp part then get giants belt and build your rylai's whice will slow enemies so you can kill them easier.Finally lich bane will increase your burst damage,void staff is nice if they stack magic resist and rabadon's will give you significant ap.