I've found a working Dragon City Egg hack which only cost 200 gems any dragon u want. But first u need to find your facebook id and session id. Since u need to find fb id and session id download the ff.
AutoHack Tool v0.3.6 -
Note: You need FireFox 48.0 version or else it wont work and also just drag the download file to the firefox page and install the add-on. In the AutoHack Tool the only thing working as of now are gems 4/per day and finding the fb and session id. There are gold hack,food, and exp but as of now they are not working.
Then go this site -
This is the site where u can edit your hatchery, storage and etc. also for the egg hack!
This is now that i found so far and hope you enjoy and give a thanks button!