Basic idea of, create a bunch of tokens, ideally turn them into better tokens via Jinnie Fay, and then hit the creature numbers to activate Jetmir and run over the opponent. Rancor was chosen as the buff card of choice, over Scale Up, due to Bayou Groff's inclusion in the deck - it lets you get a 7/4 trample attacker onto the field quickly in the event you're not having luck with draws. This does limit the token explosion potential of sacrificing a Shambler with Tend the Pests, however, so if you want to focus on that, replace Rancor with Scale Up. Bayou Groff is included because it's an extremely cheap 5-power creature you can sac to Tend the Pests, and the requirement to sacrifice a creature isn't an issue in a deck that wants to be sacrificing creatures and tokens anyway.
There is no removal or protection in this deck, as it simply can't afford to slow itself down to pick any up. If you absolutely, positively have to include some removal, Cathar Commando is a cheap white creature with Flash that can be sacrificed via card ability to remove enchantments or artifacts, and since the deck uses Black mana, the sky's the limit if you need creature removal.
Note that the deck only needs a single red mana, solely for playing Jetmir, but you can certainly change it to use red mana more heavily - certainly, red has means of sacrificing creatures with spells, such as Fling, and playing red creatures instead of white creatures will generally allow you to be more aggressive at the cost of not being as effective at producing tokens. Akroan Crusader is a good option here, as playing Rancor onto him will get you a token, as will targeting him with either spell to be sacrificed. In this sense, he may even be better than Doomed Traveler, but this would make the deck truly 4-color instead of essentially just tricolor.
4 City of Brass and 4 Prismatic Vistas to let you search for your one Mountain should hopefully be enough to reliably provide the red mana by time you can play Jetmir. You might opt to swap in some Manamorphose in place of Corrupted Conviction, or even in place of some lands - dump 1 Prismatic Vista and all three painlands if you want to be really greedy.
This is not a paper deck, so paper cost is not a consideration.
