I prefer male dogs so I would likely get another male but as others have said, it would really depend on the dogs currently in the home.
I have 2 females right now. Holly lived with us from 5 months to 11 months and then was away from 11 months to 16 months. I was worried bringing her back because Raven had shown that she was no longer tolerant of other females. I am very lucky that Raven has decided that Holly is "her" puppy but she is not even 2 yet so I still keep an eye on them in case it changes.
Everyone in this house is altered. Females were spayed at 6 months, Male neutered at 1 yr.