Yea it seems Ring Recruit isn't worth it unless you have a good amount of rings saved up...
Back when Inami was on RR, I ended up wasting a lot of them and only got junk arcana.
For the time being, I'm saving my rings, occasionally buying 3 star weapon evolution arcana for my best characters.
Doing the same with arcana coins for challenge recruit...though, I should MLB Michida first to do all her quests
Monette's tower is nice but, it keeps giving me Soldier Enhancer III and Wizard Enhancer III...I could really use some Cleric Enhancer.