Guppies are very simple to breed, use any substrate, get a few plants for decor, fake or real, then a sponge filter and a heater to keep it around 80f and theyll breed just fine
The gestation period for a guppy is about 3-4 weeks. My livebearers usually drop only 20 or so.
Oh, and make sure to feed your guppies well and give them a varied diet. They need algae in their diet, so if there's no algae on the walls, put algae wafers in there for them. They also like mosquito babies if you can find them.
What I would do is buy a sponge(any kind really) just cut it to fit the intake tube on the filter,then there u go,no more sucked up babys plus it cleans the tank a little better