A coven is typically a group or circle of witches regardless of gender, so a coven can be mixture of both men and women alike. Just in case you don’t know a male with is still a witch and not a warlock, a warlock is a witch that has fallen out of there coven know as an oath breaker.
There is no correct number of people to make up a coven you may have as many or as few as you like, although some wiccan witches like to have 13 in theirs.
The idea of a coven is to share your knowledge and gain experience with likeminded people or to generate sufficient energy or power for a particular spell or incantation.
There are however many thousands of witches who prefer to be a solitary practitioner so there is no hard and fast rule to join a coven to practice the craft.