The best way to develop your skills in architectural visualization is with practice. You can take one of your designs and try to make a realistic image using Blender and your preferred renderer. What if you don't have an original design? Use a project that you like as a reference.
That was precisely what digital artist Jan Morek did with Blender and Octane Render. He took an existing design from a house-made by blank studio and made the visualization in Blender.
You will find an incredible collection of renders using both Blender and Octane Render. One interesting point about the modeling process is that all the method uses only reference photos: no technical drawings or vector references for modeling.
In the images, you can see the Maxime Residence, which is an existing project build in Thailand.