I'm Team Dragonrace-dude!
But seriously, manga/novel cliches have been that MC would always choose cute/sexy female characters over actually useful and potentially strong male characters as party members, unlike how it'd be in most JRPGs, which party members tend to be more balanced in terms of gender, and less about fanservice female appeals. It's like many authors are afraid that MC would get overshadowed by other male characters and such cliche is getting uncreative, tired and overused by now... I'm hoping to see more strong balanced parties like Overlord or Slime series, and such parties tend to give a stronger feeling of RPG.
In this series, even if the female slave is a must, MC could have just recruited both the female slave and the dragonrace slave, since the character is already introduced, the author could easily just set the story that MC received sufficient gold too anyway.