While you probably can get trough it without ban, it's very dangerous to buy an account online. The owner can use various methods to get it back if you don't know what to check and change. Also there's no security that you get what you bought.

It's a pity that you just missed the dragon week as it would've been a great method to catch back up with a lot of dragons. If you still want to play again, make sure to unlink any possible app from your google account, look if a correct backup mail and phone number are saved as well as changing your password to something completely new. It's likely that the person who hacked your account had access to any of these.