In very rough order of how valuable I see stuff:
Festive stats are always nice for level 22+ characters.
Ruby of the Vampire Slayer acts as a silver bypass gem with a bonus 1d4 Light damage. Very solid option for your main weapon if it/you don't already have silver.
Ruby of Ghostbane and all the Spectral weapons are good for levels when you don't have shenanigans to deal with incorporeal. Borderlands can cover around level 1 and level 20, these cover in between.
Having an easily farmable (and new) sentient jewel is nice.
Adding Festive Solar is fantastic for low to mid level weapons. Light is a great damage type. Perfect for a blueshine weapon to deal with oozes.
Crystalized Eternity has an expanded crit range, built in armor piercing, and crystal damage. Might not be as good as a maul in most cases but not bad at all.
Gloomy pots of Restoration and Death Ward are amazing, since you can't buy them outside of Eveningstar or Necropolis turn-ins. Sun Flasks also hit surprisingly hard. Perfect for dumping excess chocolate at the end of the event.
If you care about cosmetics, minions, and/or mounts, Night Revels has good ones. The Reaper plates and horses look great, and the Harvest set is very nice as well. Personally I used a mirror on the Death's Smile along with Cloak of Tattered Bone for my Pale Master.
Astral Projector is pretty good for a weapon based Arti. Caster Arti won't use the Radiance much, but scaling Evil damage on weapon hit is potent and having ghostly and lifesealed is nice.
Cloak of Night is a reliable backup cloak if you don't have a better one at level.
Spectre Deflector isn't a bad buckler and gives you Protection from Evil, which is nice.
Other weapons (handwraps, pick, morningstar, wands) are all fine but probably not worth getting past low levels.
The oil of light damage and alchemical bonus to light power are fine, but I mostly just use them during the event. The summoning crystals are also okay but I'd rather dump excess chocolate on gloomy pots.
The hats, robes, docents, brooms, and masks are fun but I personally don't like them, even if the clickies are potentially powerful. Too much hassle for not enough payoff.
Ruby of Endless Night is kinda disappointing. Vorpal procs never seem to trigger enough at low levels before you have speed-shenanigans, and by high levels everything is immune. Could be fun on a repeater or TWF or some other naturally fast attacker at low levels?
I don't bother with the candies since they go bad. If you spend your stuff on consumables, make it augments or pots.
If I left anything out then I definitely don't pick it.
TL;DR-
Festive stat augments, ruby of vampire slayer, and maybe ruby of Ghostbane are top tier.
Black Abbot jewel is new and worth getting at least one of if not more.
There are some great cosmetics from this event.
Adding Festive Solar is amazing if you craft gear for alts / new lives.
Spend the rest of your chocolate on potions of Death Ward and Restoration potions.
