Just a cheap solution that I personally use for these gnats is to hang squares of thin cardboard or boxboard coated with a thin layer of Vaseline.. hanging amongst your plants.The Gnats land on these and stick.Hope this helps. Ross.

Type in Fungus Gnat in the Search space at the top of the page. Many solutions but Neem Oil is the best. Not immediate relief but long term control over future generations.
Jerry

I have gotten gnats from potting soil, peat moss- had them years ago when I was growing hosta seedlings. Learned to sterilize all my soil!
There is a mosquito dunk solution you can mix up- directions are online.
Keep the top 1" of you soil dry. The larvae like moist soil.
And I use fly papers for the adults. They work great. Mount them out of your way- you don't want to get tangled in them. You may be surprised how many gnats land on them, and flies, mosquitos, moths, etc.
Good luck- they can be a nightmare but if you only have brugs, brugs are such fast growers they can stay ahead of the larvae. It's the slower growing stuff that suffers from an infestation.