whats the best way to farm these?

And to add, does anyone have some good resources for information regarding drops? I have been all over the place with different websites and many of them have conflicting info. I was wondering if there is a most reliable source I could fall back on, or if i should just keep googling and looking up as I go.

The best way to farm stygians is doing t7 and t8 hordes and opening only mats chest.
If you're too weak for hordes you can drop stygians also in pit tiers>30.
And for the rest of the items, especially specyfic uniques you can target farm them on bosses like duriel, andy, zir etc. Every of them have a specyfic drop table, which you can easy google yourself.
There was also a way to target farm specyfic kind of equipement eg.
boots, gloves etc. some kind of items should drop more often from specyfic kind of enemies, eg. Bandits will drop gloves more often, spiders boots, but im not so sure if it's still a thing after so meny changes that they made in the itemization.

Pit (was 46 tier+ or so previously) drops Stygian drops, rather rarely.
World Bosses can drop Stygian stones.
Infernal Hordes 6+ drops Stygian stones, Infernal Hordes 8+ most often.

Infernal Hordes is by far the best method to farm them.

one round of hordes at T7 T8 can drop 3-8 stygian stones

u can offer people to bring you there and u share some stygian stones to them, you get the materworking materials etc