A sprinkling of attractive gravel on the surface of the compost around a plant helps to conserve water and to keep damp compost away from the bottom of a plant but, more importantly, it makes a plant look more attractive, at least it does in the eyes of most growers.
Potting grit is often unsuitable as it is too variable in size and not very attractive (it is meant to be buried, not put on show) but if you do find some you like give it a good wash first and perhaps sieve out the finer particles.
Cat litter, as mentioned in the Compost section, probably encourages loss of water as it’s absorbent. It also looks like cat litter.
There is actually a limited choice of attractive top dressing and you will need to shop around locally. When you do find some you like, buy plenty. Changing the top dressing every couple of years can help show you which plants have not been repotted recently.
Aquarium gravel is expensive but a viable option if you buy the biggest bag. Some aquatic supply stored do large bags of what they call ‘natural gravel’ in three different grades, which can be handy if you want to vary the size of the gravel with the size of the pot (but perhaps that’s getting a bit too obsessive!). Go and see what they have; larger outlets have a better range and larger bags.
Although the colour you buy is a matter of personal taste, brightly coloured gravel is a big no-no in the cactus world!
Granite chips are used by some growers. I personally find them a bit too large, particularly around smaller plants, and they are expensive. You may find aggregate suppliers locally but they tend to be geared towards the gravel path/driveway market and won’t have smaller grades, and the quantities you need to buy may be far too large.
Pumice – the dark, pitted type, not the paler horticultural pumice, can look good too.
A cheaper option is hen flint which is quite attractive and available in whopping great bags for around £15. I used this for several years and when I got bored with it I used it to make cactus compost.
Windowsill, Conservatory or Greenhouse?
Growing outdoors
Watering
Compost
Pots & containers
Top dressing
Potting up
Fertilizer
When things go wrong