The nature of Prince August vulcanised black rubber moulds is you can cast from them hundreds of times per hole so building an army often only requires patience and metal.
Prince August has also helpfully supplied the painting and assembly instructions as PDFs on the product pages too so you can preview everything before you buy.
Remember however that these are just moulds, so you must already have the basic casting equipment and a stock of suitable metal available or buy them with these moulds. It is all available online.
Model Metal is recommended for the best detail and the least wear on the moulds.