I Friends do the next steps and you will be able to buy all the pure dragons
just need some cheat to add Gems
u'll need Tsearch: wpepro.net/download.html
1: download tsearch or open it
2: select your pluggin in "open process" or your browser
3:select hex editor
4:hit the replace in first value insert 1000 and second 0 change the value to Ascii and hit the replace all button now go to your game and open building and see all the pure dragons or buy if you have enough gems!
just need some cheat to change gems and we'll be able to buy all pure dragons
PS: before doing this refresh your game (it's only temporary)