Straight Arkham, of course.
As for cheap decks, Teen Titans without Garth, Terra or USS Argus mightn't be capable of winning the tournament, but you'd be competitive against a lot of decks.
You could build around Arsenal Abuse (Press the Attack, Twin Firearms and all that jazz).
Otherwise, I'm sure if you posted a thread asking to at very least borrow the remaining cards you need for Curve Sentinels for the 10K you'd get them. I don't have a lot of the requred cards, but I'd lend you anything I had that you needed.
Similarly, I could just lend you my Arkham deck - look above, they're odds on to win (I could also lend you Knight Light or Teen Titans, but I've already promised to lend cards from these decks to someone else if they need them, so that's not an option unless it turns out on the day that they don't need them).
Cheers.