Kleptomancy procs exactly like Sheen resulting in Ezreal being one of the biggest abusers of the proc though the use of [Q].
The consistent influx of both Mana and Health potions saves you a lot of money over the course of the game paired with a significant income from the occasional "Sacks of Gold" proc.
Klepto potions plus Biscuits means you shouldn't have to purchase many potions at all with earned gold, letting you bypass the Lending fee of Future's Market and hit item power-spikes insanely early.
Again, we're being frugal with our gold taking both Kleptomancy as well as Biscuits so that we get the most value out of Future's Market. Because of this the lending fee is drastically less impactful on your income and you can get to Ezreal's huge 3-item spike very quickly.
Ezreal probably loves CDR more than any other AD Carry does. CDR means more survivability and way more damage. The slight Summoner cooldown also provides safety in your weak early game.
If you're looking to build Iceborn Gauntlet instead of Tri-Force then Approach velocity is an interesting choice here to further chase down your target.
Manaflow band grants massive early game lane sustain when paired with the potions from Klepto. In the later points of the game when you have a stacked tear, Manaflow will refund massive amounts of mana.
Scorch further empowers your lane poke pressure when landing [Q]s. If procced repeatedly, the extra bit of damage from Scorch can add up to keep your lane opponent in kill range.