Common mistakes when rendering 3D models with Blender’s Render Cycles include mismanaging light bounces, overcomplicating materials, and ignoring sample balance—all harming quality or efficiency.
Light bounces set too low (e.g., default 3 for diffuse) make scenes flat or dark, as Cycles relies on path tracing to simulate real light.
Overloading materials with unnecessary nodes (like extra textures or mixes) slows renders without adding value.
Not balancing samples—too few causes grain, too many wastes time—throws off quality-efficiency tradeoffs.
For beginners, start with Cycles’ default bounces (3-5) and test 100-500 samples to find a good noise/render time balance.