All soil will improve if you add compost. To make compost, add whatever materials you have and layer it into a pile. Soak the pile with water and then turn it every week or more often. Eventually, it will break down into a soil-like material. When it smells like soil and is cool to the touch, it's ready to use.
Some people really like to make their own compost.
For others, it may be easier just to buy it. Either way, be generous with compost.