Given that this is a more casual deck, either Isochron Scepter, or Panoptic Mirror might be worth a shot.
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Couple of suggestions would be either Traumatize. (Great with the amount of mana you ramp in EDH), and Trepanation Blade. (Mill till they hit a land. Much fun). +1. Always like people's take on EDH mill :)
Another fun thing I like throwing in there is Thornbite Staff, and Hell's Caretaker. Infinite zombies paired with Grave Titan. Or just fun in general with Gisa.
If you are going for a moderate Zombie/Demon tribal deck. A fun card to throw in is Patriarch's Bidding.
Unfortunately because Evolving Wilds is not a basic land. You are only able to run 4 in a deck. Rather than the 8 you currently have. If you're okay making it Modern, you could always run Terramorphic Expanse. Same thing different name.
I've ran both with great success. Although my decks tend to be a tad less budget than your list. It's still good. As long as you can get the mana to pump out Jazal's ability a few times that's a win right there.
Just throwing it out there to help you out. Lingering Souls would not be legal in this deck, as it has black mana in the flashback cost. If you are looking for a dominant mono white EDH legend with some good token power. I would either run Jazal Goldmane, or possibly Odric, Master Tactician.
Just browsing. Realized that after posting. Haha
Processpony is right. You can't have opposing mana symbols on anything. Including lands. So Tinder Farm, Ready//Willing, Rubblebelt, and Irrigation Ditch are all no go's.