That's AP Ezreal!! This is a build that Teddy and Gumayusi have also tried out.
For runes, take Dark Harvest, and from the Sorcery tree, take the two healing runes, and from the Sorcery side, take Manaflow Band and Transcendence.
The build path is Manamune, Night Harvester, Lich Bane, Nashor's Tooth, and Rabadon's Deathcap. I bought Ionian Boots of Lucidity, so that I could get 70 ability haste and rotate my abilities decently.
For starting items, if you want to trade a lot in lane or play safe, I recommend Doran's Blade; if you want to look toward the future and just farm without early fights, I recommend Tear of the Goddess.
Then, pick up a Sheen to strengthen your laning phase. After that, just build the items listed above in order. One thing you need to know: once you have some AP items, it's good to trade with W-E, but of course, I recommend using Arcane Shift diagonally or to the side, not forward, so you don't get punished in the trade.
With this build, laning phase ends around the time you get Night Harvester whether you like it or not, and once you have your two-item core (Night Harvester), you become a monster. Hitting an enemy ADC or support with your ultimate takes about half their HP, and with the added damage from Manamune, Night Harvester, and Dark Harvest, you can deal high damage even with low AP.
To those who read this and try it out, I wish you good luck.
P.S. I'm a newbie writing a guide for the first time, so please understand if the writing is lacking.