Well, if you want full completion of each individual volume, then you should max Atoli out first. You won't be able to use her again until Reminisce after the crowning ceremony.
Also, you should go pick up Healing Portion and Fairy Drop at Delta: Screaming Idling Princess. They aren't in the Ryu Books for this volume, and neither is the unnamed Azul Sachem creature that drops them, so think of that field as 101% completion.
Otherwise, Zer0's guide
should provide plenty of help with Ryu Book completion. There aren't any limited time events in G.U. until Redemption that I remember, and there's only one in that game (the window of opportunity to go to Hy Brasail is very short). Just be sure to use a Lucky Animal chart from one of his Reminisce or Redemption guides instead of the one in that guide, since all three games are the same in that regard and he didn't know that at the time of the final update.