Well, gunpowder originated in Asia, possibly introduced into Europe via the Mongols who were known to use early guns, and the Europeans might have originally imported it from there. But they did begin to produce it themselves fairly early on. The first European recipes were from the 13th century, from someone writing under the name Marcus Graecus (who's recipe includes salt and petroleum). The were making it at the Tower of London by the 14th Century. Key ingredients included sulfur, which was mainly sourced from the Mediterranean, and saltpetre, which can be obtained from a number of sources. Two of the main are natural mineral deposits, which sometimes need to be refined, and from excrement, which can be processed to get saltpetre. The other ingredient is charcoal, which is easy. Tonio Andrade says that Chinese recipes for gunpowder were more variable than European ones in varying the proportions ("The Gunpowder Age: China, Military Innovation, and the Rise of the West in World History", 2017) but the basics are pretty similar to what the the Chinese came up with.