It’s completely free to register for a GameSparks evaluation and prototyping license. We provide a premium offering which includes access to the full GameSparks platform and a first-class support system as standard as well as an Indie & Student progamme which gives you your first 100,000 MAUs free if you qualify. We have lots of features including In-App purchases so if you haven’t considered a backend of your game yet, you should give our product overview a look: https://www.gamesparks.com/product/
Our ever growing documentation site provides heaps of resources and our dedicated support team are always on hand to help should you have any questions. You can get in touch with them via: https://support.gamesparks.net/support/home