Got to level 35k+ for shits and giggles, anything above zone 600 are the same. Got to zone 1000+ and the numbers are cut off. It was fun while it lasted. You gain like 1000+ levels for doing the arena thing.
Spoiler Alert!!!
6 peasants, 6 gold mines, 1 Crystal Mine/2xbag of crystals/bag of crystals and hidden gems, and 1 Parting Gift... best deck in the game. You could go less on gold mines if u really want... 14-15 cards all you need to beat the game. Worst of all, you starts with em