There is a golden rule…
You get what you pay for. That means if you buy a gemological microscope cheap from ex India you can be sure that the quality is thereafter. I use a Breukhoven Stereomicroscope for around 250$. Then i have modified it myself. Created darkfield and polarisation filter. Bought a gemtweezer and connected it to the scope. Instead of paying around 2500$ for a quality gem microscope i have spent 300$ on the scope and it works just fine.