Pauper Its without a doubt the most budget friendly format which contains only common types, from prices ranging 15 to 80
Ancient Cornucopia One of my favorite cards to run in multicolor decks due to its ability to stabilize, Ancient Cornucopia gives you steady lifegain whenever you cast a multi-color spell while also fixing your mana
The payoff you get just from this card alone is enough to make me think that youd strongly consider expanding into Grixis colors if you already have a demon tribal deck
Legendary Creature - Elemental Phyrexian Sea-Dasher Octopus Mutate (If you cast this spell for its mutate cost, put it over or under target non-Human creature you own
I think the best fodder are ones that replace themselves or have some sort of effect when they enter the battlefield since theyve already provided value coming in, so the body is fine to use going out
No matter how mana-screwed you are, thats not hard to accomplish