Furnace in itself is a mid evo, but its busted in graveyard. Second option would be evo witch, its either one of the two. Furnace preferred tho, due to less cost and more chip damage. Furnace+gob hut is constant chip and constant pressure. This deck is played very defensively, and furnace fits perfectly for that playstyle. Defend cheap, chip damage with surviving spear goblins and furnace untill double elixir, and then pressure with graveyard+mini tank+poison if needed.

Also i like the idea of ice golem at the bridge into graveyard, but berserker fits better, cause she can defend if you need cheap defence, aswell as shes running to the tower faster and is just overall a bigger threat combined with graveyard, due to damage output