A good potting mix for container plants is one that drains easily. This is because you need to water them frequently. The soil should be relatively loose and be able to allow the roots to be healthy, which means that the roots will receive air, moisture and nutrition. The soil should also anchor the plant firmly. The make up of the soil will reflect the texture and will take into consideration the mix of sand, perlite, mulch etc. The best types of soil mix contains equal parts of organic material and some sand, silt and clay. As you become more of a garden enthusiast you should consider starting your own compost.
Watch the video below which gives tips and ideas on preparing the soil. Let me know what you think