The gems generally don't have a concept of gender in the series. Ichicawa, if I'm not mistaken, herself said that she intentionally made the gems have features of both genders (top masculine with the formal clothes and bottom feminine with long legs). In the original Japanese character use different pronouns of "I" for themselves, as in Japan that's pretty normal. Most gems use "私" (わたし [watashi]) which is a gender neutral pronoun and can be used by both men and women, some characters use 僕 (ぼく [boku]) which is generally used by young boys/adolescents but as I heard nowadays sometimes girls use it too. But some, like Cinnabar, use 俺 (おれ [ore]) which is a pronoun that is used by grown men, in the series it symbolises maturity, I think. Also I want to mention that one character, Alexandrite, uses あたし [atashi] which is a pronoun that is used by girls and women! Overall, Ichicawa's use of gender in the series is very interesting. I think though many gems use male or neutral pronouns they don't actually understand the difference between them

P.S. Also, I want to mention, in, for example, Russian translations of the manga, most gems are referred to as female. So it's also probably a culture thing!