I dont use soil with premixed fertilizer in it, especially if plants are outside in the rainy season since most time released is activated by water and warm weather and I dont want them feed in winter in the greenhouses. All I get is green, strappy ,ugly plants. Some things just cant be rushed. PLants have better conformation and color if grown on the hard side. I mix soil based on the plants growth habit.

I use the plain old unadulterated sand that's in my yard. Nothing added, nothing taken away! A little Miracle Grow falls into it when I spray in the greenhouse, but that's it

I usually mix coconut fibre, rice husk, top soil, sand and chopped tree fern roots, leaf moulch, charcoal for my bromeliad. The ratio might varied for Dyckia and Hechtia.

I mix a cheap version of orchid bark with bagged soil intended for cacti & succulents. The goal is something fast-draining, so I have been known to mix in purchased sand, gravel, or lava rock, depending on the brom. When planting in the ground, I have to amend, amend, amend so they don't rot. Sometimes I just plant the whole pot in the ground, which seems to work well.

Well,mine varies with the species,and for that reason,I mix my own.The ingrediants can be Miricle Grow-Moisture Control,[which has coconut fibers,sphagnum moss,and AquaCoir,that protects against over and underwatering];
Shultz professional Potting Soil-Plus; Canadian Peat; Perlite; My own yard soil which has a lot of decaying pine tree bark and needles;and bagged sand.These are mixed to suit the species I'm potting,but this past year,I've always added sand to any mix,representing about 1/4 to 1/3 of the mix.Seems all plants root systems do much better with it.I also use a brand called 52-Mix,which I can obtain from the Botanical Gardens,and it is really perfect for just about all plants.As the name implies,its got it all.Not available in stores that I know of.
I add Osmocote 14-14-14,[or 8-8-8 if I can find it],to the plants soil mix when I put them out for the summer,and by the time I bring them in,its pretty well used up.For indoor winter fertilizing,I use Schultz Cactus liquid plant food,N2-P7-K7,highly diluted,1 tsp.per 5 gal.of water. So far ,this works for me. All of the above posts sound good too.
Bob

Straight silty sand for the in-ground plants (I live in an ancient riverbed), and a 50-50 mix of orchid bark and a quality potting medium. No time-release food. In fact, no food never ever!

I can't remember the exact recipe, but we make our own. I think it's about 3 parts cinder (preferably black, but we've had to use red lately since that's all that's available), and 1 part each peat, perlite and vermiculite. We add nutricote to it, as well as micronutrients and gypsum. Not too much, but some.

We use this same mix for everything-- heliconias, gingers, whatever. For those other things we'll add an additional handful of fert when potting up, because you want a big burst of growth on that stuff.

The only times I'll use a different mix is for small seedlings (peat & fine perlite) and Cryptanthus. The Crypts will grow in the regular mix, but I find they do better in something that holds more moisture, like sphagnum moss or coarse peat substrate.