I love Clara. It is just so classy and beautiful. I live in a very trendy city and I never hear it. Greta is one of my favorites too.
Other suggestions: Ruby, Cora, Isla, Celia, Jane, June, Josephine, Juliet...
I love Clara and Ivory is gorgeous. Here are a few more to consider:
Clara, Greta, Laurel, Hazel.... I love those names! Go for it. Clara isn't very popular were I live. I know a few Claires, but Clara is beautiful.
Popping back in to add Flora! Dont think ive seen it suggested yet. It feels similar to Clara, but is much more unusual, since you are concerned about popularity. While Clara is at #136, Flora is not even in the top 1000. It so lovely!