Since glxgears is a simple program, and it is not working @ 32bit, my guess would be that the problem isn't with glxgears.Glxgears is the most simple program to check the 3d funtionality on my machine. I'm not interested in any benchmark. At the moment I have no working 3D with program @ 32 bit.
Some help?
The sentence you wrote beginning with, "Because you have an Nvidia GPU,..." is not found on the link you provided to the debian wiki on multiarch. If you are following a guide, you should provide the link.Because you have an Nvidia GPU, you should install libgl1-glvnd-nvidia-glx and libglx0-glvnd-nvidia and all the dependencies, and also libglew needed by glxgears@32 bit.
How to add the i386 repos: https://wiki.debian.org/Multiarch/HOWTO
dpkg --add-architecture i386
apt-get update
apt-get install package:i386
apt-get install package:i386 really? is that what you typed? You need to provide the information asked to get a good answer, not a generic answer, or some advice you found on the net with no link.
If you keep it up Garry will have someone teach you to ask a smart question.