If you need bricks for a creation, I honestly would just use BrickLink. Online PaB and DBM are absurdly expensive, it's not worth it. The prices on them are about 10 times higher than what you'll find on BrickLink. A 1x1 brick will sell for 10 cents on PaB, it will go for a penny or less on BrickLink.
What I do is design my models in LDD, obtain a parts inventory of the .lxf file that's created, upload that to my BrickLink account as a wish list, and then hunt down the parts I need from various BrickLink sellers.
In my humble opinion, a LEGO gift card is best spent on sets.
The benefit of PaB is that its all there, in an unlimited quantity, so you don't have to go scouring brickset for the seller that has all, or most of your parts in the condition your looking for.
It all comes down to time you have.
