I suggest you go to Shenzhen Shuibei, whether you join or purchase your own goods.
70-80% of China's jewelry industry is concentrated there, and Beijing's wholesale goods are also produced there.
For example, several larger manufacturers.
Baitai, Hao Yue, Emerald, Jinlong and Jinye (Gold)
Aidekang (platinum, k gold)
Xingguangda, Yuan Yumei, Liang (diamond inlay)
Lu Xian (Caibao)