I agree with Lynn. However, I do not use pea gravel myself, except when I want to use the "color" to show off a particular plant. Locally I buy 5 gallon buckets of fine grade granite gravel. The size of the gravel is about 1/4" to 1/2" inch. I run that gravel through a sieve I have made of 1/4" hardware cloth so that I get a more uniform and smaller size. This is used as a top coat on most of my plants. The larger gravel that does not go through the sieve is used for other projects around the houses.
The top coat gravel gradually ends up in the soil, especially due to transplanting, etc. From time to time I will also mix some into the soil to help prevent soil collapse.
I also sieve pea gravel. The main difference between the two is that the crushed gravel is sharper and also cheaper.
I'm still on the track of a source of bulk gravel that would be finer in size. I do really like chicken grit or what had been sold as "aquatic soil" (I believe the brand was Peters, but no longer sure) but both of these are too expensive to use in any quantity at this point.
As a soil amendment for containers, I like to use NAPA oil dry that is made from fired Fuller's earth but that is also a bit too expensive to use in large amounts.
Lastly, I find that a layer of gravel on the top of the soil greatly helps keep plants from lifting in the soil due to watering.
