I was hoping that someone would be able to direct me to a site that has a comprehensive list on where to generally farm for certain pieces of gear. I get that there are some pieces are rare and can drop anywhere, but there are pieces that drop in specific bounty boxes. Like the Royal Ring of Grandure from Act 1 bounties. I would appreciate it very much. Please and thanks.
And if I may add some basic advice of where to spend your time and ressources:
1) Spend as much time as possible in Greater Rifts, which you can clear fast (aim for 3min).
2) Don't waste any ressource but blood shards on items that are available at Kadala for 25 blood shards (all armor and offhand items)
3) If you don't need anything off bounties right now, work on other areas so you can do the bounties faster and on a higher difficulty when you get around doing them.
For the remaining items, here's a list:
need a bounty item: Do that act's bounties (well, obvious).
need a specific weapon: Farm Death's Breath in regular rifts and use the "upgrade rare to legendary" cube recipe (the yellow item can be crafted at the blacksmith, make sure to craft the right type, eg sword or 2h mace).
need a specific ancient weapon: Either go the DB route (more tries required but avoids bounties) or do bounties for the expensive "reroll legendary" recipe.
need an amulet: If your spec wants Hellfire, do that event. If you need a set amulet from a class set, put your first extra item of that set into the cube and use the "set to same set" recipe until you get the amulet. If you need Traveler's Pledge, see weapons.
need a ring: Well, anything goes, 50 blood shards at Kadala is a mediocre deal, the same applies to using the DB recipe on non-weapons. But if you have to brute force a ring, do both.
Death's Breath: regular rifts, again those that you can farm fast (not T12 or 13)
yellow, blue, white mats: Go to act 5 Battlefields of Eternity and click on all those weapon piles for white items (most mats per item). Then you can transform your excess white mats into yellow or blue in the cube.
Forgotten Souls: Nothing specific, but you get the most legendaries if you follow basic rule #1.