I don't use alibaba, instead I use aliexpress, the best way to shop on these websites are as following

1. Know what you are buying

There are fake GPUs out there, they are brandless, make sure you buy GPUs that have real names like MSI, gigabyte, Asus, zotac, Aorus, Colorful, sapphire, Maxsun, etc

2. Good sellers have high reviews

Buy from sellers that have sold to so many people and read reviews of these verified buyers, if it's good enough for you then proceed

3. Stores

Few gpu official stores are available on aliexpress, for example Maxsun and colorful, they often sell GPUs at discount price but not every time, I've buy GPUs this way so it's 100% true