soil matters: why cheap potting soil is no bargain

Years ago, I inadvertently ran an experiment.  I had started 16 Oenothera (Evening Primrose) seedlings in small pots containing my usual brand of good potting soil at the time, Black Gold.  When it cam time to move them to larger pots, I potted up half of them, and then ran out of soil.  In a hurry, I zipped over to the local hardware store and bought a bag of their standard potting soil.
Just three weeks later, the photo above was taken.  The plants on the left were in Black Gold, while those on the right were in the cheap stuff.  Plants in the cheaper stuff were pale yellowish green, with leaves less than half the size of those in better soil.
There are several good brands of potting soil available these days; I use Gardner and Bloome and Gardener's Gold most often.  Whitney Farms and Black Gold have both gone through multiple changes in ownership over the years, but are probably still good.
Cheaper soils can actually harm your plants.  It is also unwise to attempt to use soil dug from the ground, bagged compost, etc. for most container plants.  Native soil is generally too heavy or too sandy for container use.  Products sold for amending garden soil are not formulated for container use, or as a sole medium for growing plants.
You can produce your own potting soil, with a bit of equipment and labor.  If you use a lot of it, the effort may be worth it.  Instructions can be found online.