Places to farm for Earth Holiday currency. Non-italicised are Earth, italicised are Neutral. Only areas with Earth enemies are listed.
Training Fields - Death’s-Head Stag; Amaranth Moth, Bumble
Woodland Path - Autumn Dryad, Death’s-Head Stag; Strangler, Wildwood Owl
Scorched Forest - Death’s-head Stag, Rambra; Extinguished Jackalope, Red-Winged Owlcat
Sandswept Delta - Shattered Serpent; Peacock Scorpion
Forgotten Cave - Centaur Berserker, Corpse Cleaner, Peacevine Aardvark; Crimson Reef Snail, Deepmine Aardvark, Venomblade Assassin
Bamboo Falls - Hainu; Tengu, Tigerblood Foo
Waterway - Dappled Seal, Greater Sandstrike; Radioactive Slime
Arena - Longneck Interloper; Charcoal Sprangyroo, Chimera, Double-Tailed Warcat
Rainsong Forest - Deadwood Boar, Proto Manticore; Hippocampus, Parda
Boreal Wood - Maned Rasa, Woodland Turkey*; Longneck Hunter, Winter Wolf
Crystal Pools - Stonewatch Prince; Almandine Sturgeon, Clearwater Oracle, Moonbeam Crayfish
Harpy’s Roost - Renegade Aviar; Cardinal Hippogriff, Dodo, Mesacliff Harpy
Mire - Poisonous Toridae; Shellion, Southmarsh Podid, Wetland Unicorn
Kelp Beds - Relic Eel; Depin, Mammertee
Workshop - Stone Borer; Sentry Squawker, Steelhound
*Woodland Turkey is not a usual enemy, only present around Thanksgiving, but its presence in Boreal Wood makes it a decent place to farm.
With the new update, Forgotten Cave now supersedes both Arena and Rainsong Forest as the best place for farming currency. You can find further details on encounter/drop rates, chest contents, etc. in this thread and the drop rates spreadsheet.