As a minimum, you need a computer running Windows, Mac, or a Linux distribution that also supports hardware acceleration. No need to worry; currently, even the most considerably old machines support this. Additionally, to target Android devices, a phone or a tablet running Android 2.2 or higher is required. In order to target iOS, a Mac with XCode is needed, and when testing on a real device, an Apple developer subscription becomes a must.
All software dependencies are free to use even for commercial purposes. However, the Apple developer license is subject to yearly payments.
Installation instructions for additional software will be provided when needed.