It's really a matter of which gold is your waifu or which golds you frequently use, or which golds you would REALLY want to bring on your Whaleship for their stage buffs.

First one, only you can answer.
Second one, this reply I posted to a similar question just over a day ago might be helpful. But, look through your squads and decide which units you feel are really important.
Third one would be Chocolate Cosmos, Lantana, Strawberry Candle or one of the following:
Convallaria, Tree Peony, Rose, German Iris or Allium. Maybe not in one of your front-squads, but starting with 20%-30% on your Solar Beam is still very useful on the whalemaps, so might as well make the best of those units.