Need Your Advice

Depends on what you want to buy? I mostly use Amazon and Ebay

Go to the Deals section on LD, see what deals you like and the online shops that appeal to you most will quickly become obvious.

When you have selected the item you want its always worth doing a google search to see if you can find the same product cheaper. Ebay and Amazon charge big fees to third party sellers so sometimes its worth checking through google search. I think onbuy charges less so if you can find the same product on that site it can be cheaper and they offer more cashback than sites like ebay and amazon through topcashback and quidco.

Depends what you want, but if you find something you want or you're looking for something specifically, once you find it do a general google search and it might come up cheaper elsewhere