For the succubus style outfit, that ingredient can usually be obtained either from Selena (Dream World, using a random number generator), available after completing some story scenes, after which the connection with Selena will be strengthened, or from L's shop (a mysterious box with a price of over 500 coins).
For a more convenient gameplay, I recommend going to the Agranor library and reading the books that are there. This will allow you to better understand the basic mechanics of the game and form optimal strategies.