The most important casting in magick is protection (defense magick in general). I feel everyone should master that before going onto other spells and rituals. The most common mistake I see people make is that they play with spells, rituals, and spirit communication, open themselves up through chakra manipulation, and then freak out because they don't know how to handle what comes along with it. When I started out, I casted a protection spell on myself daily, and practiced keeping up a shield all day long to teach myself how to cast with nothing but focus and will (without needing any tools or words). Even to this day, everytime I meditate, I cleanse and strengthen my personal protection.
I also researched all forms of protection, exorcism, banishing, cleansing, clearing, and blessing from every culture I could find! Amulets, spells, rituals, gris gris, you name it. Not to copy but to understand the link...the underlying reason why they all worked, so I could create my own. I performed some of them, to experience them--to understand how they felt, how the energy they provoked worked.
It is a fascinating and fun subject.