Some Monster Life's Inquiries

I can earn about 100k Waru per gem typically (not counting ones bought in the special shop - those are also worth 100k Waru but are pretty sporadic) so if it requires an SS combination, the gem method's probably more cost effective, cause 400k only pays for 20 SS combinations.

I'd probably prioritize reviving the ones that require special box rewards, cause those are harder to find than the regular S ranked stuff.

Also if you have something that requires a Griffey, hold onto it - Griffey got screwed up when they rearranged the monster ranks.