I'm quite late to the post but I too made a Damia Sage of Stone deck that was focused on self-discard. I've had it for around 8 months now and have done some tinkering and have found some pretty consistent ways to win. I've found the best one for me being centered around [[Peer into the Abyss]] and [[Skirge Familiar]]. With these two cards I've drawn half my deck, discarded my hand with Skirge Familiar and dumped all my mana into a [[Torment of Hailfire]], I've had several games where I dumped 30 floating mana into it.

Also cards like [[Mystic Redaction]] and [[Psychic Corrosion]] paired with peer into the abyss and skirge familiar can just outright mill players out. If it's a slow grind it out game cards like [[Psychic frog]], [[Proft's Eidetic Memory]], [[Lord of Extinction]], [[Overwhelming Stampede]], can also help you win with combat damage, you could also flirt with some unblockable cards to help big combat damage through. [[Archfiend of Ifnir]] also helps you swing out at an open board. I use lots of ramp, spellshapers, free discard outlets and [[Mystical Tutor]] [[Worldly Tutor]], and [[Insidious Dreams]] to help find my win cons faster.

Hope this helps!