Ghost mushrooms
I forget at which point you can gather them (I think it is 235-245? But I cant remember) but they took me all the way to 300. What I did was go to the cave in the Hinterlands with my bf's 70 paladin. There are 5 spawn points in the cave, but i have never seen more than 3 spawned at once. I would turn on find herbs, have the pally clear the way, gather, enter a bg (this was before que times were insane), run the bg, and when i came back 3 more would have spawned. Rinse and repeat. It took me almost a full saturday, but I wasnt chasing all about only to have someone else gather it before me.
Edit: the downside is they dont sell as well as other herbs you could be farming between 225 to 300, but the upside is location