I don’t have any specific knowledge about requirements for studying fungi, but I recently purchased a microscope and can share what I have learned.
I purchased a compound microscope from Amscope. I suspect that all current inexpensive to moderately priced scopes are probably built in the same factory in China, and then sold under a variety of brand names worldwide; Amscope is one of those. Depending on your needs you can get one starting around $200-$300; the model I purchased was around $500 about a year ago, because of recently added tariffs it would be $600-$700 now. Adding a dedicated camera will add another few hundred dollars, they have software that runs on PC or Mac. Purchasing a microscope from one of the Big 4 (Leica, Zeiss, Nikon, Olympus) would start at a minimum of over $1000.
Quality of build and optics seem very good so far. In its new condition the scope compares favorably to Leica student lab microscopes, my only recent point for comparison. It probably would not hold up as well under student lab use, but for personal use that is not really an issue.
One of the negatives was choosing which scope to purchase - Amscope has dozens of models with multiple options and it usually unclear how one differs from another. One easy way to limit the options is to rule out any that offer magnification greater than 1000x, beyond that point you don’t get any more resolving power. For me a requirement was a mechanical stage to position the slide, trying to do that by hand would be miserable. With those requirements met you still have to choose from about 30 scopes.
The biggest issue I ran into was that the scope as received was almost but not quite as described on the website (basically the lighting system had been changed but the description had not been updated). I decided this was not a big deal for me, but you might want to consider ordering from Amazon rather that direct because of Amazon’s no-questions-asked free return policy.
Bottom line, I have had the scope for almost a year and so far perfectly happy with it.