Premium ninja frag drops are pretty low return. You would be lucky to get 1 every 10 pull. You can't actively rely on collecting from them. Unless you only need a handful of frags to finish. I tend to get like 1-2 frags per 500-1000 coupons. It also takes 40K to max the tree. And the point spending is daily, so if you didn't already start, you are too late to make use of everything if you maxed it now.