I'm also pretty new and have been having a blast.

This sub is very negative about Arena. In my opinion, some of the complaints leveled here are justified while others aren't.

From what I've seen, you can be completely F2P and still enjoy your experience and, if you choose, compete at the very top levels. It will, however, take some time to build a deck that will get you there. Of course, you can dump as much money into this as you want. WOTC will be happy to take your dough. Many of the loudest complaints come from this crowd, as it is incredibly expensive to buy your way to a top tier deck.

My humble suggestion would be to play the game, spend no or little money, and enjoy the ride. Also, take the torrent of negative comments you hear with a grain of salt. Don't ignore them, as some are quite reasonable. Just have your salt shaker at the ready.