No, you don't need to subscribe to use Instantgo whether you are looking to use the platform and its different features for yourself or because you want to provide your services, expertise and time on the platform. You simply need to register to get started.
Instantgo may simply charges users depending on the actions they do on the platform, features they use and more. Those will always be presented to the user when if/when they exist. You don't have to commit to any expenses if you don't intend to use the service for a while.