Thread:Elit3Blaze/@comment-29062154-20160715042526/@comment-8642280-20160715084408

White-Wave Seashells are obtained via Area Rewards, Progress Point Rewards, Archwitch Rewards, Panel Challenge Rewards (in EH when it comes out), and in the Witch Gate.

For a newbie, I would recommend to just endlessly farm archwitches of any kind. There is no 'advice' for events such as these other than to grind a lot of archwitches.