[Mahoyaku] What Do I Do with My R Cards?

So you've gacha'd a lot, got a bunch of R cards and don't really know what to do with them. That's ok! Mahoyaku has a complex game mechanism, which keeps it fun and exciting! As far as my experience goes, there are 3 utility values to the R cards, which are written below:

1) to be sold for sugar: basic
2) to be sold for sugar: advanced
3) auto training to unlock 4komas, hence more gems.
4) Uncap materials

This is gonna get fairly long, but please bear with me.

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( What do I do with my R cards? )