What the difference between Ezreal's ADC and Blue Builds? And why the first item, even bedore Tear of Goddess and Ionian Boots is Spirit of the Elder Lizard?
The 'Blue Ezreal' build focuses around poke items, compared to the typical ADC build which would focus more on autoattack damage and less around poking with Q. Both builds are high damage, but differ on the situation.
If your team is designed around fast engages, the Blue Ezreal isn't as good as the typical ADC Ezreal: As stated before, Blue Ezreal shines when poking and/or chasing (due to the slow of gauntlet)
Many people get Elder Lizard prior to Tears due to it's decent damage and on-hit feature. Although getting Tears first to start stacking it early may seem like a good idea, it sometimes can cause you to become too behind in lane (depending on matchup) since it provides no damage or health/sustain, and therefore a lot of players opt to rush the Elder Lizard first, since it provides an easier laning phase, supplying you with HP regen and damage, for better damage trading with the opponent. It also builds from 2 longswords, so you can grab them earlier to bully your opponenets.
That being said, it is possible to get Tears first to start stacking it early, but, you might find yourself struggling in lane more, depending on matchup.
The difference is pretty much every item.
The ADC Ez build focus's on the normal ADC items, Blood Thirster, Phantom Dancer, IE, Beserkers Greaves, and Last Whisper.
The Blue Ez build uses entirely different items, Manamue, Spirit of Elder Lizard, Frozen Gauntlet, Last Whisper and Boots of Ionia.
You get the Spirit of the Elder Lizard first because it offers good regen for both mana and health, cooldown reduction, good damage, and basically a permanent red buff (albeit without the slow). It helps your Q out a lot.