Mine the Crimstone/Ebonstone blocks of the area once you find one, then take them to your main world by leaving the game with them in your inventory. If you simply have those, you're good to go on making your own Biome. There is no need to wait on a Blood Moon and buy the seeds from the Dryad. Just get Crimstone/Ebonstone and save/exit.

Seeds can be used to create/spread biomes over Grass. These include: Grass Seeds, whose purpose is to convert dirt into Grass, helping to create more Forest or other biomes; Jungle Grass Seeds, which are used to create the Jungle; Mushroom Grass Seeds, which are used to create the Glowing Mushroom biome;