I just thought of a good idea for a contest that would most likely draw quite a few people into the arenas for a while. There should be a contest called 300/30. The contest would be a variation of the 5 of 7, but draw much more people into the arenas for a longer period of time. Instead of the normal week long contest, this would last for an entire month and you would have to play an average of 10 games per day past round 10. I would propose that it not look at each individual day though since the contest would last so long. In other words, sometimes stuff comes up in the realworld that might prevent you from playing 10 games on a particular day, so you should be allowed to make those games up on other days within the month of the contest.
Now, here's my ideas on the prizes, and this will definitely draw people in to play the contest. I propose that winners are randomly selected from those who played the 300 games and should include 1x Grand Prize, 3x 1st Prize, 5x 2nd Prize, 10x 3rd Prize, 15x 4th Prize, 20x 5th Prize, and everybody else gets a consolation prize. If you do the math there will be a total of 54 prize winners, so people wont be able to dismiss the contest by saying thats alot of work for such a small chance to win a real prize. Now the actual prizes will be as follows:
Grand Prize = one set (3x) of every current card in the game (yeah, thats right!)
1st Prize = one set of a rarity 5 of your choice
2nd Prize = one set of a rarity 4 of your choice
3rd Prize = one set of a rarity 3 of your choice
4th prize = two sets of a rarity 2 of your choice
5th prize = three sets of a rarity 1 of your choice
Consolation prize = 10 point cards
I don't think the prizes are unreasonable. So, lets not have jokes posted saying, "why not give one set of every card as a consolation prize." I believe that contests similar to this will produce the desired results of filling the arenas and making the game more enjoyable to all.