I play casual also. One of the great things about Deckbox is that you can own one card PHYSICALLY and have it exist VIRTUALLY in multiple decks with out there being a discrepancy in your PHYSICAL inventory.
I have a card that is in 4 of my decks, but I only have one of the cards. We'll call it card "A". Thanks to the deck and FOLDER organization ability in Deckbox, card "A" is VIRTUALLY in 4 of my decks. So, when I want to play a specific deck, I check that PHYSICAL deck against the VIRTUAL deck I have here on Deckbox and PHYSICALLY move the card or other cards into the appropriate deck.
Hope that helps