Welcome Stelis.
An ideal breeding environment would start with only guppies, and very few of them, in a well planted tank. If your tank looks empty, the guppies will proceed to fill it in short order. If it looks somewhat crowded, the predation of fry will slow or even stop the population growth. I like to keep guppies at about 24C, 75F. Many people keep their guppies warmer but I find they average healthier when I don't push their metabolic rate with higher temperatures. Good food, lots of room, good plant cover and clean moderate temperature water will give you as many guppies as you will ever want.