To be honest as for magick being a sin that would depend on you and what you believe. Nobody can tell you that that's something you need to look inside yourself.
As for what path to follow again that is up to you. Personally I took parts from many different paths and made my own.
Here is a list of the Basics
The basics Tools,Meditation, Visualization, Focus, Moon Phases, Colors, Days, grounding and centering, power flow, Elements, Circle Casting, Charkas
This link is for the Basics