Currently Esscence reaver into manamune then Spear of Shojin, Frozen heart and lastly Serylda's grudge is the best overall one

well you could theoretically go ap but those builds are usually subpar. For mid i usually go towards a letality build. Something like Esscense Reaver - Manamune - Duskblade - Serylda's - Ravenous. But for the most part the Trinity build still works mid

Well it's an ok item on Ezreal. Problem with guinsoo's isn't that its bad but more so that trinity or navori is better. In cases where you are lacking ap it might be more viable as it build's better with items like kraken and statikk shiv. Going ER and manamune with guinsoo's is fine but i would recommend crit items instead of frozen, serylda and hydra. Kraken, statikk, bloodthirster, shieldbow and lord dominik are a few good examples of items i think would fit better. But it's definitly viable imo

well it gives you early game life steal and +80 hp after you've fully stacked it which makes it a good survivabilty rune. Looking at the two other options in alacrity which gives attack speed and tenacity which gives tenacity, you'll see that it's basically the best option of the three. You could maybe argue for Alacrity i just enjoy the early game lifesteal more than attack speed

Not really viable for the most part, vs tanks going trinity, manamune, grudge, blade usually deels more dps than divine and is a better 1 item spike