Board Thread:Question and Answer/@comment-2219588-20140708224102/@comment-25000380-20140709054756

With level up you will increase the cost as well, and if you can spare come Jewels you can buy the 1 time only +30 or/and +50 Deck cost limit (300/500 jewels if I remember right)

But as Rynsk said, Barracks are the faster way at the beginning of the game ;)