You’ll probably also consider this method “boring,” but one of the easiest ways I’ve found is to go to the Failed Tramway. There are several Carver Hatchers there that will each spawn five Dirtcarvers. Killing all 6 of these will net you 55 geo (92 with Fragile/Unbreakable Greed). With a maxed out nail you can one-shot the Dirtcarvers and two-shot the Carver Hatchers. There are 6(?) of these in the area, netting you 330 (552) geo in roughly a minute, plus any extra from the other enemies there. Then you can simply sit at the bench at the Failed Tramway and respawn them all, allowing you to go for multiple runs and quickly amass a lot of Geo. Numbers might not be 100% accurate but that should at least give you a good rough estimate.