How can i improve the clarity of my render images?
Try taking our courses over at learn.sketchup.com. Good tips there.
-For light, you need to start using reference photos so you can see what result you are after, after some time you will have a general idea of how light works in a given situation.
-For texturing, also, find reference photos of materials you are trying to represent in your model, you need to know how they look in the real world so that when someone is looking at your image he knows what it is. One common piece of advice is nothing is 100% rough, 100% white, or 100% black. After some time you will learn to bend it to your will but it takes a lot of practice. And since you are using Vray, download a material from their repository and see how they made it, you will learn a lot by just doing that. They have extensive help online for every bit of Vray and even free tutorials on their YT channel.
-And for modeling, you guessed it, find reference photos of models, closeups, and how they look in place.
Sketchup is forgiving when you are starting but as you progress your thinking is not that much different from people using Blender, Max, or any other piece of software, you will need to learn how to model more details, how to texture your model so it looks more like a real one.