This is a complete Shine A Light Quest guide in Disney Dreamlight Valley. It will provide you with everything you need to know about the quest.
The first thing you will need to do is mine to get the gems out. 
Aquamarine is one of them you need. It’s found at dazzle beach and forest of valor. Dazzle beach has a few rocks along the coast, so just go ahead and check for them.
The other gems that you need are citrine which is found in sunlight plateau and glade of trust.
After that, you will need garnet.
You can find it in the plaza, so that’s the gem you need.
Now how to get the fiber? It is found by crafting seaweed and to get seaweed, you just have to fish in the water where there are no bubbles. If you see a bubble don’t fish there, you need to fish away from the bubbles and then you’ll have a chance to get seaweed.
Each seaweed makes about five fibers. Make sure you have a fishing partner with you so you can get extra seaweed if you find it. You need around ten, maybe even twelve seaweed. So make sure you get lots of seaweed and save it if you happen to get more of it.
After getting seaweed, go to the crafting station, select refined materials, and select fibers.
Now you just need softwood and it’s found around trees. After that, craft three sunlight torches.
Now you need to talk to Mother Gothel.
After that, place the torches at the bottom of the mystic cave.
Go inside the bottom of the mystic cave. You have to place all three torches and take a picture.
Then go back to the Mother’s Gothel and talk to her. Then the quest is complete.
