A question I receive a lot is - do I need to have the big four (Italian, German, French, English) plus perhaps another (i.e. Czech, Russian) for my audition list?
As with many of these types of questions, you may get different answers from different people, but for me the answer is - it depends.
Some fachs don't have obvious choices in certain languages for instance. I think what is most important is having a list that shows you to the best advantage. Obviously, you don't want to have a list with five Italian arias, or five English arias, but I have seen a list with something like 2 Italian, 2 French, and an English.
I think a more important to remember is that regardless of language, your list should show musical, dramatic, and technical variety.