Once you have lich bane, easy combo, q, lich bane aa, w speed boost to a lich bane aa, go in until q is back up and aa to death, you can also toss a shroom down for a 3rd lich bane attack. Simple enough, enjoy.
Runes and Masteries are up to youre liking. I use Health, Magic Pen, and AP.
With the Keystone Deathfire Touch to add on to youre Es added magic damage through your aa's