Advice? DON'T DO IT!! DON'T DO IT!!!
You'll end up spending all of your time cruising craft stores and second hand stores looking for stuff, and then the rest of your time at the vise creating things!
You'll spend all of your non-existent 'extra' money on materials and containers to store them in!
You'll look at pets "differently" and slow down when you see roadkill, wondering if it's still fresh enough to bother with...
You'll spend HOURS trying to CONVINCE YOURSELF you're SAVING MONEY by not buying flies...
But you'll and end up instead CONVINCING YOURSELF that you are able to tie things you CAN'T BUY and that you'll tie things BETTER THAN most of what you can buy (and you'll be right there!)
Get ready to immerse yourself in an art that you'll never walk away from, and if you do, and you've properly prepared and stored your materials and tools, you can return to at any point in time, and take it up again... I started when I was 9 years old and 48 years later, I'm still putting thread to steel.
As for books and you tube, books are great for lists of materials and examples of flies, you tube and SBS videos help too, but there's nothing that substitutes for the tactile experience of putting your hands on the materials and visualizing what you can do with them...
And if you REALLY WANT TO LEARN HOW TO TIE A FLY, and I know this is gonna sound weird, but it's the truth... stand BEHIND A FLY TYER AND WATCH OVER THEIR SHOULDER. If you watch from in front of the vise, you never learn how to seat a hook in a vise, which hand to hold what in, how to apply materials and keep them from spinning away from you, how to "size" materials to a hook...
I didn't know how important this was until I wanted to learn how to tie a Sawyer's Pheasant Tail Nymph. I had watched one be tied by a master many times and couldn't get it quite right. Finally he said... "Come stand behind me and watch" and it was amazing how clear it became!! Many thanks, Andre Puyans... my 13 year old self will never forget that lesson (and many others after)