My first meter was a $12 job from the hardware store down on Cherry Street and it read "wet" for three days straight while my basil slowly turned yellow. Turns out the probe needs to go way deeper than you'd guess, like 4 or 5 inches down, not just poked in the top inch of soil. Now I stick it in, wait 30 seconds for the needle to stop moving, and check two or three spots per pot because the readings swing like crazy near the edges. The other thing that saved me was bottom watering, my tomatoes stopped getting soaked once I let them drink from the saucer instead. Those cheap meters aren't useless, you just have to learn their weird habits first.