I buy a lot of precuts because I like to use a minimum of 12 prints in my quilts and I cannot afford yardage for that many prints.
I buy a lot of batik jelly rolls and fat quarter packs by designers like Janet Clare.
I generally stay away from charms and layer cakes. Not had a good experience with them. Also I hate pattern repeats. Don't get that in Hoffman batik rolls or fat quarter packs.
Yardage I buy for backing, borders, sashing.