I use pieces of shade cloth, but a piece of window screen works by far the best. Do not use rocks.

How much water are you adding? What plants are you growing? How big are the pots? What is the soil mix? All that matters.

I have 12" to 18" inch resin pots (all with saucers)

Miracle-Groî Potting Mix.

I have an assortment of plants

The potting soil is 2" below the rim of the pots. I add water until it spills over the rim and, when the soil absorb that water, I repeat the filling process two or three more times.

If it were me, I'd rethink the medium I'm using and go with something more sharp draining, with larger particles, better aeration, and more room for error in watering.

Pieces of screen are what most of us use for drainage hole coverage in containers. Don't introduce another layer by using rocks... that will work against the idea of drainage by creating a place for moisture to hang up... called a perched water table.