It's always a male name where I live; the female equivalent is
Lesley, and for a few years it was frequently teamed up with
Ann or
Anne to make Lesley-Anne.
I knew a British family where the father's name was
Leslie. His son
Stephen had
Leslie as his mn, and his daughter
Janice had the mn
Lesley. Their mother was
Gladys, which didn't feature anywhere.
I prefer
Leslie and only like it on a boy. But I don't like it enough to use.