Doran's Ring is gonna give u enough mana regen and health to stay at ur lane until u have enough gold to go back and buy your next dorans and Boots of Speed!Most likely you 'll have gotten a kill too!The thing in lane is u last hit creeps with auto-attack and harass with Noxious Blast!Noxious blast deals TONS of dmg early so get them low with harassment and when they are low enough you place a miasma behind them and keep spamming Q and E until they die!Flash and ignite can help on this a lot too!

At this point Ull most likely have gotten a kill or two!1 really importnant thing about the build is Rylais Scepter!You might want to take it 1st instead of Rabadons!Rylais may be the most imba item u get on cassio!With it u can kite ppl insanely and deal tons of dmg while having some survivability but still, the slow is the most important aspect of it!With your E with its a single target spell u slow them a LOT and with Q u gain extra speed!What else do u want to kite ppl!

Late game is where your ulti is gamechanging!Really!Succeding your ultimate is like taking a game alone!If the game takes long you can sell your Dorans rings and get 2 other items of your choice!There are many items you can buy there!Most of the time i get a Zhonyas Hourglass and a Void Staff!