is there a way to farm the red octagon coins

[Dreamwaltzer]

As the title says. Anyway to repeatablely farm it?

[Azaréa]

Nop, but you do not need to farm them anyway, if you complete the map you'll have enough to buy anything

[Gem of Temporarity]

You'll be getting them contantly if you keep going new places and destroying things. In the offchance you're lacking them for the last ancient tablet before going to the very last dungeon, you'll get enough in it. There's excess so some sources can be missed without consequence.

[d00m10rd]

i currently have an extra 63 of them after all upgrades, maybe there are more i have yet to find

[Zérodaim]

There is no way to farm them repeatedly, the best "common" ways to get more is to break pots (shops all have a few coins for you) and beat strong enemies. Later areas will give more coins, like a dozen at once near the end.

If you want something earlier than that, the first update added a really solid boost of like 65 coins hidden in the covfefe jar. You can find it in the tutorial area at spawn, but you need the third dungeon's skill to reach the hidden area in the wall.