Add a second coat when that dries, mixing it up with more colors. You want the goggles to look like aged metal, so they need a patina. Think about the materials you want this to simulate and how they look. Well-used metals are polished on the raised portions where fingers rub against it but dull in the crevices. To achieve this look, put your dark color on first, and then put the lighter touches on after the dark color dries. Apply copper patina in splatter dabs instead of a solid layer. You could use a small sponge to do this, or try applying some and then quickly removing it using a wrinkled up paper towel.
Solid gold doesn’t corrode, but gold leaf or gold plating will show signs of wear, exposing the metal or wooden base materials. (The weight and expense make solid gold impractical, even on old time fantasy objects.) To create that look, apply a darker color or different metal as your second coat. I also like to go back with a little bit of black to add shading and depth. You can take a lot of lessons you learned from painting miniatures and apply them here. If you didn’t paint miniatures, now you know why you should have.