An understanding of all the cards is another great aspect for being a great arena player.... If your new and don't know any of the previous cards from previous expansions well you probably are going to be picking cards that you know rather then don't know or never played with. A good hard study of the selection of cards from all the current expansions will help you understand the cards better going to said arena. Like I don't ever play constructed so I need to learn the cards before going in to a arena or even just test them.