I've got two gerbils at the moment, two boys, and I've found that the boys fight less than the girls that I've had, and have been more docile, but then again I had 3 girls a few years ago and one of them was more friendly than the ones I've got now.
I don't think it matters really, as long as you get them used to people and being handled from when you get them you should be fine, they arent known for biting - but be careful they sure are fast! And mine seem to scheme together so that when I'm focused on one the other can make an escape attempt so you have to keep your eyes on them lol