I decided to create this short list because i for one had to learn this by chance. So here it goes.
Non Gear Items
They drop from assasinations (third tab in the battlegate) any will do but iirc higher assasinations give more (need to test this)
Wisdom Stone / Talisman of Wisdom
This one seems to only drop (for me at least) in "threats" which are the 3 misions you see in pantheon on the right side of your screen (warning, these can be pretty hard so you'll probably will only be able to finish these later on when you have good gear).
Idols of Wisdom
You need previous "talisman" in order to use this. Can be found in lvl 41 to 50 patrols and expeditions (survival will not work seeing these spawn in a battle arena randomly).
These are easy (hunts, the game will tell you about these iirc) so just farm hunts to get these.
You need previous "sacred offering" to unlock these. can be found in lvl 41 to 50 assasinations (not sure though) patrols and expeditions.
For starters i suggest getting lukien to lvl 30 and get the following build (credit to thyworm for this video).
With this build you'll be able to unlock endgame and so legacy 7 items without any problems (enemies won't be able to touch you)
What do you need for legacy 7 items?
First, legacy rank 7/8 wich you can get by leveling most characters to level 30 (not all because you won't get to legacy 9 atm no matter what you do)
Then you just farm the highest possible mission above level 40 you can (level 40 missions still give me L6 items so) difficulty doesn't affect quality, just quantity.
Shroud cages will give you recipes but are pretty uncommon and somewhat hard to find. So to find these do missions above lvl 40 (no survival as i don't think they can and will spawn there seeing it's a battle on it's own, like battle chests, normal battles, etc.)
Also, you can reforge, forged items (and legendary items even uncrafted it seems).