I do not think I have seen this post yet(other people have probably done this and was afraid to post this feeling stupid)
I wanted to buy some gem animals.(had gotten a 25.00 itunes card for birthday).
I carefully planned the animals I wanted to buy to use up all the gems . I though okay I will buy two of each so I can breed later.
Come to find out to breed gem animals you have to pay gems(1/2 of the original cost of the animal)
so when I wanted to get my babies I had to pay more gems.
If you have limited gems just remember this when buying the animals.