Everyone is going to tell you to start with Dark Side of The Moon. They’re not wrong but be sure to be ready to really pay attention to it. Don’t be distracted, have plenty of time to ponder it after and for God sake’s don’t try to sync it with Wizard Of Oz (ever it’s not worth it). Don’t read the rest of what I have to say until you listen to it.
Depending on how that made you feel should determine where to go next. If it felt like they were playing with your heart strings as beautifully as they did the guitar sit down and listen to Meddle followed by The Wall. If Dark Side of the Moon felt like a message from the cosmos channeled and encoded through music explaining the secrets to living life check out Animals. If you were just mainly comforted by the music until a lyric sparked an epiphany in your soul you should immediately listen to Wish You Were Here followed by Momentary Lapse of Reason. If Dark Side Of The Moon made you not stop contemplating life, the universe and everything check out The Division Bell followed by A Saucerful Of Secrets, More and Obscured By Clouds. If while listening to Dark Side of the Moon you thought something along the lines of “Boy I wish I was riding a missile through space while listening to this” check out the 2nd Disc of Ummagumma (the Live Album) and/or The Piper At The Gates Of Dawn. At some point give all these albums as listen. I’ve been listening to most of them pretty heavily for over 20 years and hear/feel something new almost every time.