As an Xbox Live Gold member, you will already know about the Games With Gold program which grants you four free games every month. With today being November 1st, this means the first two games are now available for you to download completely free of charge.
Trackmania Turbo is free to download for Xbox One between now and November 30th. Click here to claim it.
Nights Into Dreams is free to download for Xbox 360, and Xbox One via Backward Compatibility between now and November 15th. Click here to claim it.