I think we talked about these before but Exsanguinate and Elixir of Immortality seem like they deserve inclusions. It's not like the list has much room so I'm unsure what I'd slot out for them...maybe Vision Skeins and Blood Scrivener. Elixir prevents a self-deck, Exsanguinate is just a great card that gets you breathing room.

Tainted Isle, Tainted Peak, and the Panorama Fetches are all cheap manabase upgrades. Fast Lands and Check Lands are also really low right now. Meteor Crater is less than a buck and fantastic in 3-color. Buried Ruin and Reliquary Tower also seem good and cheap. Mikokoro is $4 but fits the plan perfectly. Are you playing Dimir Keyrune over Darksteel Ingot as a way to punch through a bit of extra?

Yeah, keyrune with a whispering madness or stolen identity cyphered on for double the fun.  Plus it gives mana.