Saturday Dual GM Planescape 5e
Coin for Knowledge
Buy Their Book!
Well only if you want to…
First of all WotC is now once-again selling pdfs through rpgnow.com/drivethrurpg.com.
I’d recommend starting off with the core setting if you want to get a feel for Planescape and then looking over the Factol’s Manifesto and Uncaged, Faces of Sigil.