OK I created the Astrologists Lab, I picked something & saved it, explored & didn't find what I saved at the Astrologists, currently want mutagen because I got 2 bad results for a unicorn I want to improve, all her battle stats are red. So I changed my item to mutagen, again haven't found any, does this thing actually work or is it just a waste of time & gold? If there's more to it than just picking & saving an item then what else should I be doing to get results?

Mutagen is a rare item. Two explores are often not enough to find some of the ordinary resources while certain Premium Shop items has significantly less probability to be found. As it's explained in description, Astrologist is multiplying the chance of finding an item. It doesn't raise it up to a fixed large number. For example, if the chance of finding a certain item is 1%, level 1 Astrologist will raise it to 2% which is still one of the 50 chests in average.