only spend them on weeks that have Fukurokumaru Deals. And even then, spend it in an event with both a wheel/board and a redeem feature (like Lucky Board, Lucky Stars Wheel). Spend for a meta ninja and then finish off the rest of the coupons for training potions til you get the max tier of the Fukurokumaru deals (or work towards another ninja).

This way you get to maximize your coupon spending. You get 2 new high tier ninjas, and a lot of power items both from fuku deals and the event you spent in.

Never spend coupons outside fuku event.
Spend in konoha tree, great plates or lucky board if you can because when you do you're getting passive power every time you spend, and then you will get whatever redeemable prize you wanna have.

What i would do since is the start of the server, get your carry already, with 20k you can get edo minato for example, but that depends on your likes man go check ninja list and read 'em up, then go for the one you like. If the server would be more advanced or you would already have 1-2 good ninjas then my advice is go full power spend.

Thats is such dumb thing suggest. Spending in Konoha Tree or Lucky board is good idea only if you plan to recharge a lot. Great plates can be a good spending event if there is a good ninja as a reward.

I would suggest you to spend 25k (if you can ) next week. Fukurukumaru deal reward for 25k spent is edo minato. So instead of spending CPs to just get minato in Konha tree or Lucky board you can get 100 frags for free from Fuku. You can spend all Cps in Lucky stars wheel or the Colored Banner Gift. Going full for lucky stars is maybe better idea because you can get potions every time you spin, And you can exchange lucky stars points for even more potions and command flag frags. So for 25k you will get some crazy power boost and you will get amazing ninja at same time,

IF you decide to spend 20k and get only a ninja you will lack power later on.

i have 50k coupons. was expecting a good 40k fuku.