What should I spend grinders on?

[Bassz]

I just found out what it is, and I think I have about 20 of them. I don't want to waste them. Also, I'm assuming "dei grinder" is the weapon/armor grinder, and I don't know what Mono Grinder is for.

[Mike]

Monogrinder is for 1~3 star items, Digrinders is 1~5, Trigrinder is for 1~7. Use them on whatever you like.

[Bassz]

Wow, thanks a lot!

Just realized, it's probably supposed to be "Di-grinder" or something...

[Moniker]

And don't sweat what you use them on; they're actually pretty plentiful in the game. You can also purchase them with Photon Drops in the Underground.

[Bassz]

Cool :)

I have collected only about 15 Photon Drops so far, but I haven't started any hard missions yet anyways. Thanks Moniker.

[_Vyser_]

I usually spend them on 5-7* weapons that have really good percents and armor with 3-4 slots. Don't worry about wasting them, I have so many thanks to the achievements and doing so many Tower runs.