Hi, there's a few things you can delete from your vault. Here take a look:
https://imgur.com/a/8EZXcca
I marked with a red "x" the items you can throw away.
If the weapon boxes I highlighted in orange are from dungeons below lvl60 you can also delete those. You can open the ones highlighted in green (radiance stones chests) and equip/store the radiance stones in the second tab of the Unity window (ctrl+h).
I've also noticed that you still have some remnants from last event that you don't really need anymore, so my advice is that you exchange them in the Dragon Express.
Oh! And you can store your outfits in your wardrobe (F3).