In your case, D'art is a good choice, since the assault SR weapon from dark's daily raid is a gun and you don't have a weapon for Modred so far.

This thunder event is one of the worst in terms of rewards. So just grab the AP potions, some Soul P, and as many copies of eido as possible without spending AP potions. It's not a strong eido, but still useful for beginners.

The Jack-o-Lantern event, on the other hand, is one of the best. Jack-o-Lantern's 45% dark atk boost is higher than any other event eidos. The SSR and SR weapons are also quite nice.

Next dark hime will be Osiris, coming along with Light advent event, likely in late November.