I finally beat the Gilgamesh trail woooo!!!
it was a hard fight and took me a few attempts but I managed to get everything in one of the rounds bar the Atk 30% reward (party of 5 or less), I think it took me over 30 minutes to complete. There's a definite emphasis on survival in this battle rather than full on power and bringing more support units than damage dealers is key.
I went in with Rain equipped with Dual wield Excalibur and survival edge and kept using Lava Floor to seal Holy, Earth. Fire and Wind damage, I normally wouldn't use Rain but this is one of the challenges where he's a niche unit because if you equip him with DW he can seal 4/6 elements. I used Orlandeau and divine ruination as my main damage dealer, I brought a friend noctis to use Thunder flask to seal Thunder, the only element I couldn't seal was water but it didn't do too much damage.
Support units were Cecil for Provoke plus extra Curaja, Refia with Dual Cast Curaja (finallt put some of my Trust moogles and got Ludmille's dualcast) and buffing...she's a better option than Rem because she has embolden and Full Raise.
My final support unit was Ling who was just amazing, she can dodge, Regen MP, AOE Esuna and revive and debuff the girl is just amazing!!
Just kept evade up on her to dodge attacks and used Invigorating Dance to heal MP for the team and Chakra for herself to heal MP and she can revive all KO'd units too. She was such a lifesaver, I couldn't have kept up without her and wouldn't have completed the No item challenge without her and Get Bushido freedom she's amazing as a support unit I'll be using her for more trials in the future.
Also went into the ELT against Wilhem in the new event, he was a tough cookie, needed a good debuffer(Noctis), buffer unit (refia) Bushido freedom to dispel the buffs he gave and to go in fast with Damage units, it took me a good few attempts and party reshuffles to knock him down, he goes a bit mental on the attack after you get him down past 50% hp. I don't think I'm going to go in for the 4 party challenge, I'm not crying for a 15% MAG ability.
EDIT: FUCK THAT FUCKING DARK ESPER TRIAL! I killed Ifrit, had Siren down to about 20% HP and the fucking bitch heals herself to full and goes on the fucking rampage and one shots my party!!, I was a good 40 mins into that trial, fucking absolute ridiculous mechanics in that fight.