But the question is, what do you want to buy online? There are online stores dedicated to a niche.
Homeshopping.pk is the name I trust when shopping online for mobile phones and other stuff, I had a problem with one of the things I bought from them, but the way they took care of my problem was amazing!
For anything related to computers (laptops, accessories, PCs, etc) I only trust Galaxy.pk, they have the best prices and warranty, been buying from them for over 10 years now.
For cheap Chinese stuff like toys, mobile cases, car accessories AliExpress.com
Edit: and yeah tcsconnect.com, haven't bought anything from them, but is a name I would trust.