If you want more creatures, you can put some of yours in your duplicates and trade them against other creatures own by other players. The game is based around trading, so the main way to gain more creatures is by trading yours ^^
Each day you can go to Games -> Glade and unlock a present. After 30 days you have access to the Glade and have 5 minutes to adopt a creature you like (they are from old deleted account, cheating account, ...)
https://gothicat-world.com/glade
You can have more creatures by using the gothimorphosis (in the adopt section, you have multiple options, the free one require you to go to the mine during each connection to collect a crystal (you can have 1 crystal a day). With 30 crystals you can create a morphosis (it's a fusion between 2 creatures chosen randomly in the game). So you can totally create destrinos morphosis (but you can't trade them).
https://gothicat-world.com/gothimorphosis/mine
At lastly, to earn more creatures, you have two majors events during the year : Gothibirthday (in the begenning of June) and the Snwoball battle (during december). For these two events, you have to collect either pie or snowballs and throw them against other players of the game. If a player shot you successfully, you will receive a present and you have the possibility to win a creature in this >:D
I hope I explain it greatly, my english isn't the best ^^'
Oh and lastly, is it possible for you to put one of your creatures in your dupplicates ? I want to send you a welcome trade ^^
