Achieving a higher level of realism

Greetings! This is my first topic here as well as the first post but u gotta start somewhere.

Recently i started my first bigger project and i wanted to discuss general problem of achieving a higher level of realism in cycles scenes. After trying everything to improve the quality of my materials, models, scenes i must ask You for advice. How to make this scene look more realistic? Im planning on making an animation of a mysterious crime scene. This is the result so far.Most of the lighting here does not come from emissive objects but from fake area lights to decrease render times but now comes the problem. If i add rain here as well as some atmosphere all the fake lights come to attention. Is there a way to disable the light influence on atmosphere only for speciffic lights? Also what are Your tips on optimising such scenes. Keep all modifiers as not accepted? Keep all objects separately or join some of them? Rendering in separate layers obviously but maybe there is something im missing. Let me know what You think!