I was able to put together a decent starter kit for a friend for under $20 from mudhole. They have some kits as well you could use and build on, or just select the individual pieces you want to get started.
Like fishing gear, you really want to be working with a decent set of tools. I use a Danvise ($89) because it can handle size 20+ nymph hooks and 4/0 saltwater hooks. It's also the least expensive true rotary vise I could find. You also want a good bobbin, one that has adjustable tension so you aren't breaking thread all the time. Other tools such as bodkin and whip finisher can be had for short money. Then you'll need materials...