The nurseries are bulging with lots of different soil amendments that you need for your garden. How do I choose? These are a few:
Lets start at the top with sphagnum peat moss. This is always a good amendment to the soil as it allows air spaces and holds moisture, both needed by the roots for a healthy plant.
Next is red mulch or black. The question should be what is it made of? Is it wood, rubber, other materials. If the label doesn't tell you, don't buy it. Also, if you can't resist the red color, wear gloves when handling or you will end up with red hands!
Pellitized gypsum is made for a special use. It does 2 things: it provides calcium and sulfur (which are minor plant nutrients); and it improves soil structure by helping soil particles clump together. This, then, makes it easier for roots and moisture to move down into the soil. It is often used on clay soils, but best to use according to a soil scientist's recommendation.
Concentrated Compost sounds good. Organic matter (rotting plant material as leaves, lawn clippings, garden refuse, manure, etc.) always improves the soil by increasing soil structure and nutrients. Its best to read the label to see what is in the bag. If it is made from sewage, you will not want to use it for your vegetable garden as it likely has some heavy metals. It would be ok for shrub border.
Mushroom compost is a good choice for many gardens. It adds nutrients and organic matter to the soil. Mushrooms are grown on manures, hay, cotton seed meal, corn cobs and other organic material. After the mushrooms are cropped, the compost is left. This is what you are buying. It is rich in organic matter and nutrients. Use this sparingly and dig it into the soil. It may have high salt levels, which can kill young seedlings.
Some amendments referred to as soil conditioners have different compositions. It is best to know what is in it. The red and yellow bag pictured above includes mycorrhizae which promotes strong roots. I'm not sure about bat guano and worm castings. They should probably be used sparingly as they are probably high in nutrients. I would check the bag to see if nutrient analysis is listed. The blue bag of soil conditioners is natural, organic, and retains moisture. That part sounds good; but what is in it?
Top soil is what we all need. But, again, what is in it? If the label doesn't list ingredients, it may be dirt scraped up from a construction site, not any better than what you have. Using appropriate soil amendments can help you build top soil, a valuable resource. Good for your garden, good for the environment. And like many things, it takes time.