Ideal is used as a noun and not as an adjective ideal = a standard or principle to be aimed at
So you only have one. That's sad. In translating the meaning rather than the words it would probably be better to say "What are your ideals?". Duo accepts this; I just tried.
Isn't this sentence supposed to be in plural? What are your ideals? I never heard someone say "what is your ideal?" unless ideal is revering to something like for example "what is your ideal marriage ? " or something like that