What are the best legendary celeste quests to farm?

Since the Halloween Event is currently running, I recommend doing the following quests, because halloween gear is only available when the event is running.
List:
Witch Way to the Village (optional is mandatory)
Tomb Sweet Tomb (can ignore optional)
Mummy Issues (skip optional)

Legendary quests (when you run out of those repeatables)
All the halloween legendary quests except Dead of the Night


But obviously after Halloween Event goes away, you'll have to farm something else.
My list of permanent quests to farm:
All quests imply optional is completed. You can forgo the optional for now if you struggle, but just know that LFGs usually expect an optional completion.
Repeatables - City:
Persian Coercion (start out slow and take out bases one at a time) - Carthage / Delos / Farafra Oasis New Pharaoh's Challenge (more micro heavy, very rewarding, wall off obelisks) - Carthage / Delos / Farafra Oasis
Median Manipulations (Persian Coercion but Babylon themed) - Babylon
Temple Wrecker - Babylon
Ambrosia Obsession questline - Babylon

Elite Quests - City:
General Zu, What did you do? - Babylon
Red Dawn - Babylon
Lots of Rogues - Argos
Losing Your Religion (ram rush enemy TC) - Argos
You Complete Me (co-op only, rush first 2 tcs and build up) - Argos

Legendary Quests - City:
The Renegade Escapade Grand Finale (spear only) - Cyprus
More Mad Medians in Mesopotamia! - Babylon
Liberating the Village of Sais - Rhakotis
Liberating the Lower Nile - Rhakotis
Come Together - City of Rome
Visiting Calydon - Athens
Visiting Corinth - Athens

 

It may seems a bit odd but with the new star system of chests the best way to get good items or gold is learning the 5 star quests and do 2-3 a day. Besides Valley of Kings i think they are all pretty doable. Search for good players and add them to the friends list so you can find someone to do the quest. I just feel the lower star quests don't give good enough good items

 

They asked for quick and easy quests, 5 stars are neither. But yes. they are rewarding.

 

Impossible Cata - it's not hard
the old MS Legs, pathos etc. - not hard
Elite - Rescue me , in fact all Argos elite's are easy

 

I wouldn't recommend Beorix Returns (an old MS leg), because it is quite difficult, but I agree with the rest.

 

With some consumables (what can you use EP for ?) Beorix can be managed .. but Ok it's challenging, tbh I forgot that one .. thanks for pointing it out ...

 

Well , what do you use EP for ???
I use them as an EP soak ... I still have 10's of thousands of them

 

After you bought all the permanent stuff like shops and more empire vault space, i use it for decorations and most for rerolling in sparta for better rolls for expensive items like mag, master bow etc.

 

I use it either to reroll gear (I usually save them to see if new event gear is rerollable at the start of an event), buy decorations (I buy carthage houses), or skip annoying quests.

 

I buy labour of the empire .... and the one that gives a massive boost to resource and priests

 

Was it ever possible to reroll an event gear to lets say a stronger zahak sword etc?

 

Yes, they sometimes let them slip through the cracks. Zahhak sword specifically never was rerollable, but there were instances where a nerfed zahhak sword was given out by devs. But there have been multiple times where event items had been reforgeable, since event items have to be manually added to the blacklist to remove their ability to receive reforges.