What do I do after I completed campaign? Just started playing and killed the act 5 boss.
Also if anyone has some cool free hand-me-downs that would be awesome.

Once you have completed the campaign once, you can just ignore that part now. Adventure mode is where you will want to play. Hand me downs are a no go as there is no trading in-game unless they are legacy items, or you happen to be in the party when the drop happens, which initiates a timer on giving the item.