you can get a free set for each element by leveling up your player level. Then the rest of the toys can only be purchased with real money.
There used to be a mode called Pussy Market which alternated with the new girl event and you could buy toys with the event currency. Last year the dev removed it thinking the game was too free-to-play-friendly. If you go to the toy screen and a description says the toy is obtainable in pussy market, that means it can only be purchased with real money now. I happed to started before the last pussy market so I had one set of those pussy market toys.