Depends on what your looking for I think!!
Atelier Pierrot has a lot of gothic brand pieces iirc, but obviously since it's brand its pricey.
If you're looking for something more affordable, then taobao is the answer. There's plenty tutorials on how to buy directly from taobao, or you can use a reseller (I wouldn't personally reccomend this, since they tend to increase the original pieces quite a bit, though you can use them to look for pieces and brands you like).
This is a good list of shops to avoid. I cant list all of the best but these are some of the worst.