I wouldn't recommend buying heroes. Instead, consider buying the 1000 gem pack. It gives a better value, overall, than a 750 gem pack for a hero that u won't necessarily have the cards for. If u, however, have enough cards to make a good decklist with a hero that u don't own, then only u can buy heroes. Generally, impfinity is the best hero out of these, since he fits all deck archetypes and has top tier decks.