Personally, it’s good to see that you have created your own flooring, instead of using a flat part with a material on it. Also, the lights that you have are really nice too, you might just want to minimise the glow by adding a very transparent SmoothPlastic part below it with the Institutional White color.
I would recommend looking at creating the ring more inviting, by adding in some chairs, tables, pictures whether necessary. You could also look at other showcases and get some tips for how they effectively create an underground feel.
Overall, it’s a nice build, and with some more added details to give it the desired vibe, you’ll be on your way to having an awesome boxing venue!