For my .02 cents, look at Springfield leather for sample packs of tooling leather
http://springfieldleather.com/30018/Pieces%2CTooling%2C2-lbs-Bag/
They are inexpensive, MUCH better quality than Tandy and a great company to deal with.
Tandy is a good place to start out with tools, courses and leather, but as you move away from kits and want to do your own custom stuff you will want to move to higher quality tools and better leather. Still, Tandy does a lot to get people interested in leather work
Cheers and best wishes