If you trust in the theory of gambling, then it's not that bad, actually. Basically, if your chances to win are above 50%, then it's worth the bet. And that rule holds true all the way to SSR slvl19, since you still have ~52% success chance.
... of course, the theory of gambling doesn't apply here since it assumes you get double back when successful, but in Kamihime you only get 1x return when successful. So with your gains halved, you're never above 50%, really Yes. If you can be bothered, make some of your R fodder slvl3. I'd recommend sorting by Lowest Atk, and you'll always find the leveled up fodder from the front and non-leveled up from the back.
SSR slvl 10 -> 11: 19 slvl1 Rs + 1 slvl3 R
SSR slvl 11 -> 12: 18 slvl1 Rs + 2 slvl3 R
SSR slvl 12 -> 13: 17 slvl1 Rs + 3 slvl3 R
And so on.