Add depth of field, bloom, and grain
Effects are the seasoning, not the meal. A strong shot with restrained effects beats a busy one every time. Here are the three that give you the most polish for the least effort.
Depth of field
Depth of field blurs everything that is not at your focus depth, just like a fast lens. It separates your subject from the background and quietly hides flat or busy areas. You can also rack focus, shifting the sharp plane from one layer to another mid shot to move the viewer's attention.
Bloom
Bloom lets bright areas glow softly into their surroundings. A small amount makes highlights feel like real light instead of flat white. Keep it gentle. Heavy bloom turns artificial fast.
Grain
A light layer of grain adds texture and stops large flat colors from looking dead and digital. It is one of the quickest ways to make a clean render feel filmed. A little goes a long way.
A note on restraint
Pick one or two effects per shot and keep them subtle. The goal is for someone to feel that a video looks expensive without being able to point at why.