It's a lot like the tabletop. I wish most people understood how the game is played; this isn't Hearthstone. You start with one of the basic decks, accumulate cards and experiment with adding or subtracting cards from your deck. The game gives you around 500 cards for free, once you reach level 25 (takes about two days). So unless you're a munchkin who wants to copy successful decks found on the internet, if you're playing for the fun of it, MTGA is brilliant. I don't like comparing it to Hearthstone; the latter is a lot more casual but provides a different kind of entertainment - like Naxxramas.
And remember: even the best deck can just give you 25 lands cards in a row. Go in with an open mind and start with a conservative deck that you actually understand. Then you'll be able to get better.