BDM, Most folks either start off with leather gleaned from the local charity shops (Old boots, handbags, jackets and the like) or they get their supplies from places like Le Prevo or The Identity Store.
Both of those companies are also good for the tools you will want (as well as many other places, of course)
As for the tools themselves, you probably have some that are good for the job already. I'd recommend starting out with...
A "Stanley" type knife,
A Steel rule,
Good cutting board (doing leather work on an unprotected dining table tends to lead to problems with SWMBO)
Waxed thread,
Suitable needles (Leatherwork needles are NOT sharply pointed like sewing needles but are more like a "bodkin" type as you are effectively only using them to pass through holes already made)
A #2 Edging tool (best all-round size to have)
An Awl,
A stitching wheel,
Adjustable stitch groover.
A piece of bone or plastic for burnishing edges with,
fine Wet-n-dry paper for sanding and smoothing edges prior to burnishing.
Check out the various "How to" tutorials on the site and have a go at it ! Any problems, give a shout and there are plenty of folks here who will come to the rescue.