I went on a local wedding cake icing course, which explained basic techniques like stacking/pillaring, swags, roses, and how to get good piping. Course cost me about £20, buying a stand cost me about the same as hiring one, and the (three tier) cake itself cost me about £30 in materials. All in all, about 1/3 the cost of a bought one and I got precisely what I wanted. I used my mum's wedding cake tins (one of which hadn't been used since her wedding!) and had a great time decorating it.
Of course it set me off on what has since proved to be a great fun hobby and I have definitely spent more than the other 2/3 cost on equipment etc!
You can get plain cakes, choc or vanilla, from supermarkets - I helped out a friend who bought her cakes like that, then put my icing flowers on it. If you're putting anything wired or fresh on a cake, make sure they're not poisonous! (Euphorbia is pretty nasty that way, for instance, but seems to be in a lot of bouquets.)
Recipes - I'd get a Lindy Smith book, as she gives all her Madeira etc recipes at the start, for all different sizes and shapes of tin.