Bettas are extremely difficult to breed:
1) You need good breeding stock. Many fish sold at fish stores are too old already to breed.
2) They are aggressive. Males and females don't get along, so getting them to successfully mate can be difficult and you need to have an appropriate breeding tank for them, like a 20g long, with a divider and plenty of hidings spots.
3) You need at least a 40g breeder to raise the young fry and then house the females until they are large enough to sell.
4) You need gallon jars for each male (this can be hundreds of jars in a single spawn). Each jar needs an airstone and needs regular water changes.
5) You need live foods for the young fry, as it can be difficult to get them to eat prepared foods.
6) You need to find homes for all of the fish you end up with, which can be difficult.
So, in other words, to successfully breed bettas requires a lot of money, time and space. If you're interested in breeding fish but want something a little more interesting and challenging than livebearers like guppies, I suggest trying one of the easier to breed cichlids like kribensis or, if you have a big enough tank, convicts.