I am new to this hobby and was on the MMS website trying to make a list of oils/butters to buy. But looking at the selections and seeing that most of the products are available in both oil and butter, I started wondering if I should get the oil or the butter or do I need both. Can either be used for all products or do some products always require oil and some always require butter? Can butter be melted to get oil? Suggestions on must haves is also very much appreciated. Thanks, Emily