@Igor Here's some thoughts on improving renders that I tell my students:
There is no substitute to education as spending time in the software. You just need to build and render as many scenes as possible. Every days and quick studies have been instrumental in my learning - and a lot of them fail or never see the light of social media, but I still learn tons from them. It takes a lot of time - learning the software is only part of the journey.
Lighting is key - beautiful topology and hyper real materials will all be useless if the lighting is off or bad. This is the number one thing I see in renderings that need improvement.
Imitation is the best way to learn at first. Too many people try to take on learning 3d or improving 3d and being a designer/photographer/stylist all at the same time. I suggest that you find photos that you like and try to reproduce them. This way you have a specific lighting goal in mind as well as architecture or design choices are minimized and you can focus on your craft. Later, you can design it all, but while learning - only take on one thing at a time. See attached - I still do this regularly to try and improve. I take liberties and change things around a bit, but the general look and feel vibe is already established. This is key.
(this might be a great challenge too - post a photo and see if beginners can try to reproduce it. I have my students do this with modern kitchens.)
Keeping in mind that I teach film and stage designers how to render - I think one should look to film lighting as the inspiration for making images. I think people get too tripped up in trying to be mathematically photo real, so if the sun is at this level and the window is this tall and the light should hit the wall here and then it should look real.... This is not how photographers and cinematographers work. No photographer for Architectural Digest goes on a shoot without a full set of lighting equipment. If you study film lighting, you will see that the proximity and the scale of lighting in film (HUGE) is used, even when subtle realism is involved. So I say study film lighting more in depth. See attached examples and take a look at:
http://mattscottvisuals.com/lighting - a great resource that shows the lighting layout for advertising shots.
There are lots of Instagram sites dedicated to film lighting and BTS setups like @filmlights and others. Subscribe to these and study the rigs.
Hope that helps some - always happy to share my settings and lighting setups for any images I post if folks are curious.
-evan
Thanks! This is great to look over and see how you set up all the loops.