If you place liquids like water on succulent leaves and leave them exposed to the sun, the water could act as a magnifying mirror and burn the leaves. If you're using leaves, ensure that you get the whole thing. Make sure to get the rest of the pot as well. Fungus gnats are attracted to moist soil containing lots of plant matter and leaves that have been decayed. Keep your pot dry and clean. Soil is a key factor. This is why it is so important to make sure that the soil is fully soaked. Water should not penetrate any deeper than the soil's top two inches if it is very small.