Evolution items in Pokémon GO are required for you to evolve some of the Pokémon in the game. Without them, you’re stuck with the weaker version of a Pokémon you want to make stronger, and they usually have a threshold to how useful they are before you need to decide to use something else. A great evolution item you should be on the lookout for is the dragon scale. Unova stones and the Sinnoh Stones are some of the rarest to acquire, though.
To acquire the dragon scale, the easiest way to get it is to find it by spinning PokéStops. You can find these all over your city, although some areas have more of them than others. You have a slim chance of a dragon scale dropping when you spin the disc, though. The more PokéStops you visit and turn to receive items, the higher chances you have of receiving the item.
Alternatively, you have a chance to acquire it by completing the seven Pokéstop streak, but it’s not a guaranteed thing to drop. But it doesn’t hurt to try and increases your chances whenever possible. You might have the opportunity to acquire a dragon scale from special events that developers Niantic host throughout the year in Pokémon GO.
Beyond visiting PokéStops in the game, you don’t have too many other options available to you.