I think that statement hoop earrings are better than smaller ones that have a tendency to look a little chav. Wear silver or gold, thin hoops that are very large and wear them as a statement piece. Keep the rest of your jewellery simple so no necklace or mutiple bangles.
I think hoop earings should only ever be worn with your hair loose, if your hair is tied up they can look very chavy/gypsie-ish!! I definately agree that statement hoops are way better than the smaller hoops, esp with your hair down as the smaller the hoop the less your going to see it.