If you want a real render in a small time, you are in the right post.
This render need the Default Scanline Renderer selected (by default) in the Assign Render subsection (under Render Window -> Common).
For the first step you need to remove all lights from the scene and add only a Skylight. Set multiplier of the light to 1.0 (default).
Nextly in the 'Render Window' go to 'Advanced Lighting' tab and choose under 'Select Advanced Lighting', 'Light Tracer' (Active label checked).
Now you are ready to render. In you want more Antialiasing, go to Antialiaser tab and check 'On' under Global Ray Antialiaser. Now select Fast Adaptive Antialiaser (default).
If you want more Shadows you can add another light (such as Target Spot) and decrease Skylight multiplier (For example Skylight multiplier 0,6 and Target Spot multiplier 0.5 is a good compromise).
Below an example with Light Tracer and Skylight rendering:
