Keep shrine maiden Dianthus for a 16' stone. they are very common, espacially with Whale Medals. If you have a ticket to choose ANY 5*,it's better to pick a recent girl (2017, 2018 or 2019 one).
Rice Choco Cereal Lily Friti new year is a good idea. she is not bad at all. Another good girl is Straw Flower. Solid girl and her Sun Altar panel are very helpful at the begining (espacially for Whale Ship).