with guppies, you have to decide if you want to try and line breed them for whatever characteristic you want, or just let whatever happens , happen. plenty of videos out there on line breeding guppies. better fish is in the eye of the beholder. pure strains certainly have the eye appeal depending on what it is you are looking for, however mutt guppies will tend to be more robust/healthier. 2-3 pair of guppies, or mollies etc will have you up to your ears in fry in no time.
i recently started or more correctly restarted something similar. i gave away my old strain of guppy/endler hybrids, and got a pair of blue dragon guppies, and a pair of yellow dragon guppies, and 2 young female red dragon guppies. i like the dragon type of guppy, and time will tell what colors show up. good luck.