With the new improvement on the Great Konoha Tree, every spin guarantees 1 coin, which actually makes in some cases a good investment, depending on what you are looking to do. Of course, the more you invest, the greater the returns, but with the new update to the tree, you get free draws that gives you guaranteed coins, plus every investment gives more coins than when it originally came out. You do not need to max the tree to take advantage of it =p

~Jib