I got my first Guppies because my very loving nephew thought he was doing me a favor. That turned into about 500 guppies quickly. My males will squabble from time to time but I have never noticed much damage to each other. If you keep both males and females, it won't be long and you will be over run with them. I have sold a few hundred to the pet store here to keep my numbers down. Actually, traded for other fish, fish food etc... Unless you have homes for them, I don't recommend getting both male and female Guppies.
They are beautiful fish with delightful little personalities. Admittedly, I really enjoy them but... I recommend an all female tank. All of my females seem to get along fine and without any males, you won't have the population issue. Females are not quite as bright as males but I do have some very very pretty females as well.