You don't need multiple core sets to get started. The core set will come with a total of 350 cards containing 5 heroes, 3 villains, and a lot of cards to build your decks. You're able to use 4 heroes in a game, so you'll have 1 hero that you swap in after each game. The core set will allow you to play solo, two players, three players, and even with four players! However, if you want all players to be able to play with the same aspect at the same time, you'll need to have more core boxes. But you'll usually be fine with just one core box.