Does putting gravel into the bottom of a pot really make it drain better? Actually, water in a container filled with just potting mix will drain quicker than water in a same-sized container with gravel in the bottom half.
In the pot at upper right with gravel in the bottom, water will actually slow down as it passes from the finer-textured mix into the coarser-textured gravel. The result is the roots, which grow in the upper part of the mix, will stay wetter. This could be good for plants that happen to like wet conditions. But it’s bad for most plants that need good drainage.
So for the best drainage, skip the gravel. Cover the drainage hole with a pot shard or piece of window screen (to keep the potting mix from washing out of the hole) and fill the container up with just potting mix.