So I tried the open beta and all I can say is that people who pay exorbitant amounts of money for cards are jerks. other than that it is fun, give it a shot since it is in open beta.
you get a free pack every couple of days from completing quests so you don't have to spend really, but it does help i guess. i'm getting them a little slower than that though because i'm play the arena with my gold which is 150, but you always get a pack
I've also been playing the arena, The way I see it is the actual entry is only 50 because I get the pack plus if I play well I can make up that 50 anyways so there is no reason to buy the packs.
the most i've won in the area is 5 games, but one of my losses was a DC, and that sucked. i got a pack, 1 card and 50 coins, so idk if 4 win is exactly 50 but thats the free-est arena i've had