For what books to look at:
Shadowrun 20th Anniversary/ Standard Core Rulebook : Well its the core rulebook.
Runners Companion : Gives an expansion on several areas but most importantly for you, I imagine, is the plethora of new qualities and the extra metatype options.
Arsenal : Guns, Drones, Mods, and all things explosive. You will find something shiny in here no matter what your character.
Augmentation : Cyberware, Bioware, Nanoware, and Genetech (For when what god gives you, just isn't good enough.). Not as useful for Mages, Adepts, and Technomancers, but then again you never know.
Unwired : If you want to mess with the matrix then this is for you. Lots of extra goodies for Hackers, Technomancers, and some bits and pieces for Riggers.(Depending how dedicated you are to the role)
Street Magic : If you want to sling spells or use adept powers, this is the book for you. Not alot of use for non-magic characters though.