How far are you from All Shapes Bonsai in Ringoes? By far, for someone just starting who wants a decent first material, the best place to go is a bonsai specialty nursery. They'll also have tools (most of which you will not need), books (buy as many recommended ones as you can), and materials in all stages of development.
If you're looking for an indoor tree, I'd recommend a Ficus or Baby Jade as a first tree.
For outdoors, either Cotoneaster or Juniper.