Its a clich? I know, but making mistakes is the best way to learn - I recently had a 120# Pacific yew warbow crack and break on the tiller the other day. Not the most enjoyable moment of my life, but because it happened I've learned a few more things that I hadn't tried before, so it's all beneficial!
Just to echo and reinforce the other guys' statements - there is definitely a point where you should stop reading, and just crack on with it. Reading/videos is fantastic - there's also nothing like being shown by somebody who really knows, but when all is said and done, it has to be your hands that learn it for real, and that just means getting on with it and inevitably making horrific mistakes, so that you can use the lessons next time.
Del's blog is excellent, as is Alan Blackham's DIY PDF "the back street bowyer" so have a flick through those, perhaps go as far as getting The Traditional Bowyers Bible Vol 1, and that should see you through.
As for materials - I started with ash, and promptly wished I didn't. It's awful to work, and may well put you off as it's so unforgiving and needs quite a deep understanding of techniques such as trapping, heat treating and perfect tillering to make a really good bow - it will make a poor/mediocre bow, and will of course teach you lots about the tools and techniques, but starting with something like hazel or yew (not too hard to find if you have some patience!) will probably make it more enjoyable from the beginning. That being said, I'm talking purely from the perspective of making English longbows - ash doesn't really like that design, whereas it's pretty damn good for flatbows or pyramid bows.
Another option is laminated bows - you can either buy very good laminated staves online or through a dealer, or just make up your own - all the materials can be easily bought from a timber/hardware shop (you want something like elm, ash or maple for the backing layer, and lemonwood, yew, oak, ipe, osage etc etc for the belly) and you just glue them together with a good quality resin/URAC glue and from there, you can almost make a bow by numbers, especially if you have access to tools like a linisher or bandsaw.
As a personal preference, I would suggest you start with a good quality board of hickory, red oak or ash from a timber supplier (make sure the grain is as straight as possible, with no knots or flaws that you can see) and lay out a good pyramid design (tonnes of pyramid bow dimensions and build-a-longs can be found online) as this style of bow is the most forgiving in terms of tillering, and is very easy to adjust to your own personal draw weight. You should have a nice bow before you know it, and then you can apply your newly learned skills to more challenging staves or bow types.