There are a handful of ways you can acquire new weapons in Genshin Impact. You can use wishes to purchase a variety of items, along with potentially receiving a new character you can use in your party. There’s also the chance for new weapons to drop off of creatures and from inside of chests that you can find exploring the wilderness. Alternatively, you can go to the primary city, Mondstadt, and speak to the blacksmith at the city’s entrance to have them create new weapons for you. But you need to perform a quick task for the blacksmith first.
When you initially speak with the grumpy blacksmith, they have you locate chunks of iron ore so they can use it to create new weaponry for your characters. You can find these chunks of ore almost everywhere in the game. All you need to do is find the side of a hill and look for the large rocks resting on the side. You can hit these using any of your weapons to steadily break them. Once their health is gone, they break down to become a type of ore, most commonly these are large iron ore chunks. Acquire enough of these, and bring them back to the blacksmith.
Share the items with the blacksmith, and he can now make your weapons whenever you have enough resources. A majority of the weapons he crafts for you will be available after you receive certain items. Many of the better pieces of equipment are accessible after you defeat bosses, so you need to take on powerful adversaries in Genshin Impact for the blacksmith to have the correct ingredients to make some good weapons for your characters.