I love the name Ruby and while I'm not usually a fan of changing the spelling from the traditional, I do like the idea of Rubie. I think it's still very pretty and makes it a little bit more unique, as I do know of a few little girls named Ruby.

Even when you have an easy name it gets misspelt by people who haven't a clue; I am Jo and you wouldn't believe how many people spell it Joe. I would have thought it was fairly obvious that a) that's the male spelling and b) last time I checked I was not a man.

Choose whichever you like best in your heart and good luck!