All you need is something to put whatever it is you are selling into. For me, I usually sell books so I make sure to have plenty to small boxers and perhaps some bubblewrap.
For shoes and video games, you could use a shoe-box or even those envelopes which have bubble wrap inside them. If you want to get boxes, bubblewrap, and tape, you could get them in lots of places, such as Walmart.
Hope that helps :)