I nearly always opt for a plain black nail varnish, as I know it's going to match whatever I choose to wear. Dark reds, purples and blues are a good alternative if I have a specific outfit in mind, and this collection has them all.
There is no single brand of perfume which is the definitive gothic scent. There are a few which include patchouli, clove or incense aromas which can make you think of funerals, but choosing which to wear, if any, is a very personal thing. However, there is at least one perfume that's black.