Sometimes! You can get Magic Gathering codes in certain physical packs of cards.  Buy any recent Planeswalker or Prerelease Decks, or Starter Kit or Secret Lair pack and it will come with some sweet codes for the corresponding deck on MTG Arena. Just be careful. Only buy packs released after the Ravnica Guilds. Earlier decks don’t come with any codes. When buying Starter kits don’t go more than a couple of years old or the Magic the Gathering Arena codes inside may have already expired.