Arrtx 120A Marker Set (they have many sets, not all have metallics in them so make sure it includes gold and silver if you choose a smaller set. 60A in the dark blue box also contains gold and silver).
I mentioned the Arrtx 120A set because Arrtx has lots of different packs, and not all of them include metallics. If you want those Christmas-y gold and silver details, make sure the set you choose actually has them (the 60A dark blue box also includes gold and silver). Metallic markers are such an easy way to make ornaments look more festive fast.