So, where do we start?
The most basic piece of terrain that you will encounter in gaming is the figures base. To start a base, one needs to gather a few materials.
I usually start with fine grain sand - the smaller the grain the better. Then I add several different sizes and colors of ballast in differing ratios depending on what effect I am going for.
Playground sand is good - however the smallest container I've found it in is a 5 lb bag - more sand than you will ever need for basing or other projects, so I pick up a container of craft sand from my local craft store. Its cheap, fine and comes in 1 lb bottles.
Next I raid the Woodland Scenics shop - and start mixing in ballasts. From small to large, it all goes in the sand, up to and including one or two pieces of Talus - there are occasional large rocks mixed in everywhere you look.