I try look for higher sold numbers and review amount. Than looking for the sellers rating and also numbers.
A lot of brands have official AliExpress shops which you can reach via their website.
On the other side, get yourself a limit you're comfortable to "lose" and buy expensive stuff locally.
Hey, i just sent the request for your deadlock invite.
If valve didn't change anything it usually takes 1-3 hours and you will get an email/notification in steam when you're able to join.
Cheers, have a nice day and feel free to remove me as a friend when granted access.