Even guppies benefit from a good varied diet, including live food and veggies. But note that all live food does not necessarily have to be live- as in swimming around in the tank- there is a lot of nutrition in frozen or jellied live food. Also, things like infusoria (for small fry) are not difficult to grow- a banana skin in a glass of water; I did this when I was 10.
Anyway, if you are going to breed- have you got grow-out tanks? And, just as importantly, have you got somewhere that will take your fry? Judging by the number of very young bristlenoses seen in the shop around here, they are overrun with fry from people who haven't got the space to let the youngsters grow out to a decent size at home. If you run out of homes, have you got the space to separate the male and female? once they have got the idea of breeding, they may want to carry on.