Focus on your basics first and the concept of magic. Don't worry, you'll get it.
I believe you're referring to blood magic. It is a form of practice that some people use, but some don't as blood is never required. In fact, you can practice magic without anything, though herbs, crystals, and some tools are helpful and really give you a boost.
Focus on your basics first, before diving into anything for sure. You might find you still are interested in blood magic, but regardless, you need the basics for anything to work.
Nope, a lot of people don't even use blood in their magick at all. Those who do, do so for a very specific reason. It can be used to empower spells or as an offering to a deity or spirit. But think of why you are using certain tools and materials. If you don't have a reason or need for it, don't do it.
Just like using herbs, stones, or moon phases, if you do not know what they are used for or what they represent symbolically, why would you be trying to use it? Hearth/Rikki gave you some fantastic and informitive links worth reading, they will help you get a basic grasp of spellwork. But don't stop there! No matter how long you've been doing spells, rituals, and whatnot, there is always more to learn.