I have cousins named
Gillian and
Jemma :)
I like
Gillian, although it is a bit dated (more to the 1950s and 1960s) here. I also only like the G spelling.
Gemma is also dated as it was really popular here (I live in the
UK) in the 1980s, and I don't really like it. I guess it would be fine in the US though as it's not so common there.