I would go for magatamas as well. I've been playing on S1: Naruto since it opened on July 20th and I'm a F2P. As of right now, I only have like 2/3 level 4 magatamas that you can get from quests and what not. I would say the coupons are better to spend on getting your stats up.

For me, refines are good but the problem is that they don't always work. There is a failure rate. So I say the importance is:

Magatamas > refines > other events (like moods). I wouldn't buy any scrolls since it's never a guarantee of anything good sadly. One day in the future hopefully they'll fix this.

Sorry not a Midnight Blade main... XD

If you were water, then it would be +Nin, -Atk. It depends on what you want for your main.