I literally suck at arena. I always go 0-3. Sometimes 1-3. I'm still a new and only rank 18 on constructed. Am I better off just buying packs instead of entering arena?
Probably best to use some kind of tier list for the arena if you're new or you'll end up with some grim decks. Keep mana curve in mind also.
Watch youtube/twitch arena players. There is a bit of a knack to it.