Glissa Sunseeker

• WWizards of the Coast2004-12-01
  Official Ruling
  You need to have the unspent mana before the ability resolves. The ability doesn't allow you to activate mana abilities while it's resolving.
• WWizards of the Coast2004-12-01
  Official Ruling
  The artifact's mana value must be exactly equal to the amount of unspent mana you have when the ability resolves. If there's less mana or more mana, the artifact won't be destroyed.

Rulings via Scryfall