You are talking about dark magick (in a very pop-culture sort of way). You are 13, so I'd advise joining a coven that studies white magick before you start dabbling in things that can too quickly get out of your control.
Elements would be earth, air, fire, water and if you count soul or spirit as 5, then that one as well. Shadow isn't an element, it's a lack of light. It's darkness. Darkness normally represents evil or ignorance. (ignorance isn't evil, so darkness isn't always "bad.") Some use darkness to describe something they see as good that others generally see as bad.
It may be easier if you list the things you want to do with "shadow magic." The way you are talking it sounds like you want to learn the way of the ninja, hiding in shadows or something, or dark magic.
This is what I tell anyone wanting to learn any kind of magick:
First learn that magick works from the inside out. Second, to take control of what goes on out side yourself, you must first take control of what goes on inside of you. Third, you take that control by practicing every day. Lastly, you are always where you should be, don't rush the path. Magick of any kind comes from you learning how to control and manipulate your chi, or chakra or your energy. The best way to do this is through meditation. Once you control the flow inside of you, you can start using it to control things outside of you.
Hope that helps, if you want something more specific, please be more specific.
I work with shadows. It's boring personal development stuff, like catching that you're getting defensive about something and wondering, "Hey, maybe it's because I'm wrong." Creating a safe space to wonder about that, and letting your ego die.
That's called a Shadow, the concept that the thing your ego loves most could be wrong, and admitting that you're wrong is one common act of working with the Shadow.
Admitting that you're wrong is too high a price for most aspiring magicians to pay, especially if you expect a minion to form and do your bidding or shadow portals to physically take you from one place to another or something...because that doesn't happen physically. As mentioned above, physical shadows are just an absence of light that we've turned into a symbol.
In the otherworlds and astral planes, the same boring personal-development shadow work that I mentioned can get fun...and by "fun" I mean "horrifying".
Just play a round of Shin Megami Tensei: Persona 4 and get back to me if you're still interested in doing something like that for real. Well, for ethereal.
