I am going evens on the roosters/goats since they have rare gold item drops. I am hoping the rate is like the Pot O Golds, I manage a gold item weekly on all accounts if I remember correctly.
For these type of event prizes, I think it's almost impossible to finish unless a few gems are spent. I decided to get an extra fountain. It seems if I can get a jump ahead early in an event, I am much more likely to be be able to finish & get the final prizes. But these are worth it IMO.