Genshin Impact: Yae Miko's Ascension Materials Farming Guide

gamespot.com:

Yae Miko, Grand Narukami Shrine's high priestess who moonlights as a light novel editor, was made available to pull in Genshin Impact's 2.5 update. If you've obtained her, then you're ready to embark on the long arduous journey of building Yae Miko ready for combat. Below are all the resources and their respective locations for Yae Miko's ascension and talent upgrade materials.

An electro catalyst character, Yae Miko can be made your main DPS--in that case, get her to level 90--or a sub-DPS. If she'll be support on your team, then level 80 is good enough, especially if you're F2P and are low on resources. If you're a newer player, you'll need to wait until you've unlocked the Inazuma area to level Yae Miko up.

If you haven't emptied out the Souvenir shops yet, you can purchase a limited amount of Vajrada Amethysts from those locations. To farm for Vajrada Amethysts, you'll need to pick a fight with one of the following normal bosses: the Electro Hypostasis, the Thunder Manifestation (Electro Oceanid), the Bathysmal Vishap Herd, and Primo Geovishap (if infused with electro).

The following weekly bosses also drop Vajrada: Dvalin, Childe, Azhada (if infused with electro), and the newest Raiden weekly boss.

For farming Yae Miko ascension materials, I'd suggest going for the Bathysmal Vishap Herd boss fight. You will need to fight the vishaps anyways for another ascension material drop--Dragonheir's False Fin--so you might as well kill two birds with one stone.

Plants that grow near the ocean, Sea Ganodermas are plentiful across Inazuma. My own personal farming recommendation--if you're pressed on time and just want to efficiently farm one location--is to go to the Nazuchi Beach Overlook waypoint and head north to the beach