Just been muling things over (again), and came to the conclusion that I should start saving up Life Gems again for when the shop resets next month. The only things currently left in there for me are a 4* skill bloom and the ampy beasts, of which I have 16 or 17 stacked anyway, with more to come from events and farming 12-5.
It just feels like the refreshed lvl 100 manyus and especially the rainbow skillbloom will serve me much better. Sooo, it's time to hoard lifegems back up to 500 again.