Cost a lot to try and keep up and they're always changing rules with no warning. At first wasn't so bad but now ridiculous. They change upgrading randomly as well. For example you upgrade your dragon. This requires dragon stones. Well I was waiting to up upgrade until event to get discount on stones. Well they changed rules and now it will cost $200 to get my dragon where I could have easily upgraded to before for free and thats just one thing you upgrade!!! Customer service response, so sorry!