The question of Aurumoth I've got to ask is, "Is Aurumoth" as a pseudo legendary a "good type", like say Dragonite is, is one that's more sort of creepy?, like Spiritomb is?" Given it's psychic and bug types, I'm leaning a little bit towards the latter - so suggestions for a few "weird" type moves I think are in order (especially going from its artwork) - although these do include some current signature moves;
Crafty Shield, Eerie Impulse, Forest's Curse, Freeze-Dry, Magnetic Flux, Nuzzle, Phantom Force, Topsy-Turvy, Trick-or-Treat, Aurora Veil, Instruct, Laser Focus, Prismatic Laser, Psychic Terrain, Shell Trap, Spirit Shackle, Spotlight, Toxic Thread.
A few of these are already mentioned, but a few aren't. Spotlight, for example, follows on and matches from Tail Glow - it's from that, combined with it's nature as a precious metal, I've tentatively included Prismatic Laser (arguably worse than Psychic given that it cannot act afterwords), and Laser Focus to represent more direct "beams" of light - it already has Solar, Ice and Hyper Beam after all.
Nuzzle and Magnetic Flux are slightly strange options - but given it already has access to Thunderbolt/Thunder, while Eerie Impulse is a throwback to not only it's Ominous Wind, but also the suggestion of including Pressure, despite being an Electric Type move, gold is after all highly conductive. Following on from Ominous Wind - that's also the suggestion for Phantom Force, as is Spirit Shackle.
Freeze-Dry follows on from Icy Wind, and Aurora Veil combines with some of its "weirdness" aspect in its ability to manipulate weather slightly - it has Sunny Day, Rain Dance and Hail after all, so being able to mess around with the upper atmosphere as a Psychic Legendary seems to fit.
As for the rest of the weird moves - Forest's Curse, Topsy-Turvy, Trick-or-Treat, Instruct, and Psychic Terrain all being possible options to put this across - manipulating typing, other pokemon's actions, their stats, or simply the actual battleground in itself.
And what this leaves is Toxic Thread Shell Trap, and Crafty Shield - which was intended to suggest how it makes it's cocoon, using Crafty Shield to avoid the Poison from Toxic Thread. Would suggest if these were to be included, they were from a previous evolution for flavour use, in order to protect the previous metal from which it was made using Shell Trap. Crafty Shield being Fairy Type could fit in with Fairy Wind and Dazzling Gleam if those suggestions are included.
I personally think that between its current move-set all of these moves have preferential options, apart from niche applications of Freeze Dry, and Prismatic Laser, and maybe Spirit Shackle to Psychic Types (despite that Psychic Type unlikely to remain in due to having 1/4x damage vs Aurumoth anyway.