Noob Item Questions

What are the big items for each role? To my knowledge the roles in this game are AP, Mage, ADC, Support, Tank, and Bruiser. Is there a general set of items for each role? For support the big ones (To my knowledge, i swear there were three though) are Spellthiefs Edge and Ancient Coin, so for other roles are there a handful of noteworthy ones to swap depending on character, build, etc? Before someone says it, i know, context matters. Every guide on gear that isn't specifically a build for x character in x situation says context matters then proceeds to say nothing except what each stat is for the entire guide. I really need to know what items are big for each role so i know what to build toward, then i can learn the best ways to get there efficiently.