You can feed it any cheap food of the correct type 2 Stars and below (ie you can buy distilled water if it likes drinks from moogle (dragons like drinks), or hare meat if it likes meat).
Once it hits 2.5 fives just feed it evolution food until it evolves (except for some of the most expensive things I read wait for Elasmoth until its 3 stars?)
I've never had to feed anything with expensive/rare food more than 1x fortunately, but some of the cheaper foods sometimes it takes a few days before it will evolve.
The Cacataur has been a pain for me (I'm on my 3rd one it won't evolve into 3rd form, I couldn't even get 2nd one off baby for some reason).