For buying supplies and leather, Tandy is a likely if not exactly cheap choice. I just recently got started as well and noticed early on that anything marketed for leather craft will carry a premium price. The same thing marketed for a different segment may cost much less.
Some basic supplies like needles, thread, and small leather pieces will be available from general craft stores like Michaels. For many tools, you don't need a "leather" version to get started. Any utility knife will cut leather, you don't really need the $90 rounded edge version at first. A cheap mat cutter cuts perfectly nice, straight pieces of leather, I found. Many tools are optional or simply a convenience. Make your own tool combos if you can. I use a cheap metal locking clamp and two pieces of wood blocks with felt to hold small pieces of leather when stitching small pieces - no need for the $80 stitching pony yet. For large pieces, my knees come in really handy until I get a cramp, haha. Cheap tool stores like Harbor Freight (there's one in Arlington) have specialty knifes, arbor presses, and things like that.
Youtube is vital resource for me. Leather craft gods like Ian Atkins and others happily share their skills in instructional videos - their quite addictive.
I did buy one book for figuring out out how to construct bags and specifically gussets (Leatherworking Handbook: A Practical Illustrated Sourcebook of Techniques and Projects, $16 on amazon.com)
For buying larger pieces of leather relatively cheap, I've used Maverick Leather (http://www.maverickleathercompany.com/). They often have nice bargains on leather, including the famous Horween stuff. Just work around or embrace the flaws (character!) that often come with second run leathers.
Having some basic skills in a vector drawing is handy for making your own, precise patterns. I make patterns that have the stitching holes placed and spaced precisely where I want them for repeatable stitching. It takes a little longer to mark the stitching holes but is more predictable for me than using the little wheel tool for marking stich locations.
Get your hands on some leather and experiment - enjoy!