This nation certainly does not resemble anything close to be balanced. And why should a dragon nation be balanced anyway?
One thing, in addition to raise recruit prices, is to have a gold cost on all summons. They will not cost gold to summon, but they will cost upkeep. So an ancient dragon can cost over 200 (3000 gold cost) to maintain. Another thing, more powerful dragon can devour gems. (I do not know how to do it though)