This will always be a stupid fucking tip

Get proper moving boxes. With uniform sized boxes they can be stacked for storage, or carrying around and is much easier to pack in a truck, elevator, cart, car etc. When you use random boxes you end up spending more time playing tetris trying to figure out the right way to stack them.

Aside from all that, you'll need to drive around wasting time and gas looking for these boxes, since they're glued they can't be broken down so you can only carry so much to which you're just essentially carrying boxes of air back and forth. For about a buck and change for a box you can go to any moving supply or big box store and buy a ton of boxes that are folded flat.

I'm the end getting free boxes will cost you way more in time and gas.