Couldn't find an event guide anywhere, besides the 2015 wiki post that said wear event gear on every slot. Obviously it's difficult to get event gear on short notice if you don't normally collect it.
Score seems to be mostly random, I got the HQ suit on all of my characters wearing a Pitchfork, Lycopodium Masque, and Green Moogle Suit and spamming Spicy Crackers. Least lucky character took 81 crackers, so if you have some patience it may be worth just spamming with what you have and seeing if you win eventually.