Succulents typically come from dry, arid environments where rain is infrequent and the soil is poor.
These plants are adapted to small amounts of water being left as condensation and dew, or short periods of rainfall followed by heat and their roots quickly drying. Planting a succulent or cactus into a moisture retentive soil that remains damp for weeks will quickly rot the plant.
Making a good quality succulent substrate
There are many different ways to create a good succulent mix. What matters is that water drains quickly through the substrate, it dries relatively quickly even in winter or dormant periods, and that it doesn't compact and break down too quickly even in harsh sunlight.
20% good quality potting mix or succulent soil. This mix has some perlite and larger bits of organic material already mixed in, but that's not really necessary.
30% perlite. Perlite is puffed volcanic rock, it's light and won't break down and helps keep the mix from compacting over time.
10% orchid bark. The orchid bark helps create 'pockets' of matter and prevents the perlite floating to the top and soil being washed out of the bottom of the pot.
40% horticultural grit or sand. This is a fine grit which won't break down over time. Perlite is lighter than water and floats, whereas the grit is heavier. Having both ensures that with time the soil won't settle at the top or bottom of the pot and compact.
The finished mix
The finished mix. Your mix should look similar to this. It's mostly inorganic material that won't retain moisture with smaller pockets of organic soil to hold on to a little moisture in between waterings.