After about 80 failed attempts (more like 7-8) I have decided that I don't have the pieces I need to knock out all of the Gilg trial missions. Seems to be coming down to not having a mana battery (my daily reminder that I f'd up big time by not pulling Ling).
I have everyone over 4.8k HP at this point (Refia with Ramuh, Cecil with Golem, Bartz with Diablo and Firion with Odin) and good enough equips (Bartz with trident + excal, Firion with Chij + kaiser knucks and was generally taking a Noctis for redundant fire+holy coverage). I mean, there is a pretty good chance I am just dumb/bad at this game, but, I run out of mana often and any turn I take to try to address that generally means I am donezo. Plus I have had 2-3 times at 20% threshold where for whatever reason people other than Cecil die to the insta-KO then it is just overrrrr.
I think I am going to wait for Tilith 6* for the mana sustain before I try again. Assuming I am lucky enough to get her. That being said I feel like I could beat it with a full team, running a 2nd tank to throw those elixer candies at my Refia/friend Noctis but, I will feel like a loser without the 30% attk