The only thing to bear in mind is the sex ratio. Because livebearer males are completely focused on sex, they get a bit much for a single female to cope with. So you can either keep 1 male with 2 or 3 (or more) females, or a group of females only. You can also keep males only but then I would say it's best to have at least 5 to spread aggression out a bit (those hormones!). There is really no difference in attractiveness between the sexes: females are just as colourful. Even if you do get females only, they may be pregnant from the shop. Some females eat their offspring, others don't, but if you want to it should be possible to rear a few.