Save coupons and go for power items from events-myoboku packs,training potions,refine packs,charm packs,you should be able to get them with event points if you are active.Save moon scrolls for cave keys,you need 1050 at least every month.

Just get whatever is available at the events.Refines and charms had rebate event,when you get bonus for using them.Its good to save at least 500.

Myoboku,training potions,secret scroll pages you c*e right on.Cave keys have rebate too,that's why you should get 1050,that amount will give you ultimate treasure essence+more bonuses.