Bit of a disclaimer before you continue: use this at your own risk of course. Banggood can change the behaviour of their site at any time, but this works for now at least. The code is completely safe to use, it isn't a hack, it's just using the functions provided by the website already.
That changes how many banner ads the site shows to you in one go. The number 200 seemed like a good amount for me, it doesn't actually go up that high, but better to try and show more than having to go through multiple pages.
Next enter the following code:
That tells the site to load 728x90 banners. You can tell it to load others e.g. 336x280 if you change that 13 to a 4. Different numbers here correspond to different banner sizes, I didn't try to document them all.
That puts all of the banner code into the console, which you can then select and copy. The approach used here is the same as Banggood does itself so should work identically.