Spending on the lucky dice event, usually happens on the 1st week of any given month, is a great event to spend coupons on. You get items like magatama, cave keys, seal scrolls, etc. when you use the lucky dice. I usually use the points on refines and charms.

There are lots of events that can help you, both spending and non-spending events. Like what was said above, Lucky Dice or Lucky Board is a very good event to spend on, especially when the secondary prizes that you can redeem are things that you want (whether they be ninjas or medium-level refine runes for power).

What will help with power in a cost effective way is to spend during events for items such as refinement runes, Charm Materials Pack, and Cave Key Gift Pack.

Also being able to stack events and get more than just spending for what you want is always good. For example, there are events where just for spending ingots, you can get rewards. There are also events where the action of recharging can award you redeemable prizes.

Always look for stackable opportunities to get the items, then wait for events like refinement rebate to use them.

I know it is a lot to take in, but I hope it is helpful. If you need me to clarify, just let me know.

~Jib

how is your refine, magatama, purify, rune stone, charm and SA right now?
a good way to see what you're lacking is to click the *on at top left corner

In terms of raw power on long term (when your rune, magatamas, summon runes are level 4+) the best are charm materials > battle armor > tactics > refinement.

I feel that Mission Mobile Generalisation's payout is just as good as Lucky Board.

Check your power up *on and see which area you're lacking, that *on aint just for show you know^^

Thank you all for the advice. I'll keep that in mind for the future.

In addition to lucky board, the other thing worth spending on is the cave key mystery fruit.
For 799 coupon you get 88 keys, which is worth 968. And that's not all! You get a random lv 5 rune, which, on average, is worth around 20-30 extra keys (~250-300 coupon value).

Do note, however, you should not necessarily use the keys you get from this fruit immediately. Instead, they should be used during rune cave rebate event (thou the mystery fruit event do tend to overlap with the cave rebate). This is true for ALL expenditures. GETTING something and USING something are almost always separated.

Take Lucky board, for example. For the last one, in the best exchange item there was charms pack and medium refine. Which you get is up to you. But using them should fall on charms rebate OR refine wish credit event (the last lucky board happened to overlap with charms rebate, but don't count on it)
And before that (2 lucky board ago), there was medium thread, which should only be used during battle armor rebate. I'm not sure if medium thread will ever come back, I'm done with it personally but.. still useful for many.

In any case, the point is, spend your coupon to get stuff in one event and spend the stuff you get in ANOTHER event(thou the two might overlap).