It is.. /shakes head around/ ehh, you want to focus power with your coupons. Not ninja's.
So if you don't have the ninja tool yet, it'd be best to get it. Like, if they release a book, or a blade, buy it, because we don't have access to them yet because of our level. The other stuff, like, face mask, rings, shuriken, necklace. It's kind of worth to do it, but then not really, because you already have items with stats there, and the golden ones will only give you a small power increase.

If it's like 500 coupons for a golden ninja tool, buy it. (if it's any more, i just wouldn't, and would just keep saving)