That's a very good question! My SM says that "fashion jewellery is very popular" (I guess that means it sells well). I like the look of those animalier and crystal earrings (above) and would happily wear (if they were comfortable).
The aesthetic
is flashy, it's
supposed to be flashy that's why the clashing colours and the (mostly) large sizes. I don't find them any more opulent than say Chanel or Dior in many ways, perhaps more irreverent and fun.
If you like more classic, quiet pieces maybe look at some of the smaller real silver or gold jewellery that
Gucci do so well. They're made in Florance (Gucci's birthplace) and are amazing quality, materials and workmanship. You'll find they are not that much more (comparatively) than th costume.
Some RTW already has similar 'jewels' on anyway like my Animalier hats from AW and a dress and bejewelled tie from last years Cruise/Resort. These can be worn like jewellery so if you like the themes and size of statement but don't want to wear as 'bling' it can be done with scarves and belts and other a_ccessories.