I have an all male tank and a ladies tank both with a mix of guppies and platies, I prefer the platies but its a personal choice.
Even though they were separated out at the lfs the ladies were still preggo and have had fry which I have separated into a 3rd tank. It's worth considering males only unless you want to be overrun or know your lfs will take them back, as the ladies showed no interest in eating the fry for a few days before I oiked them out!
Also it is recommended that you get 2 ladies to every man as their constant and persistent desire to mate can literally harass the ladies to death so you need at least 2 so they can get a break! That does mean more fry, could be hundreds a month even just starting with 3 fish. Men are pretty and mine aren't overly aggressive with each other.