[blender]how do i improve my final renders

I would recommend improving your lighting and setup(background). Lighting plays a very important role in your renders, these could vary from stage lights to HDRI lights, it really depends what you are trying to achieve. Based on your models I would say add more stage lights and making those renders come to life.

If you want some tips you can watch this channel, he has some good stuff: https://www.youtube.com/user/AndrewPPrice

Hope this helps.