I don't think this deck needs too much explanation... it's a build that's purposely limited to $100 (our play group's challenge), and it's primarily filled with creatures that ETB with +1/+1 counters natively, and that have death or ETB triggers, plus a bunch of sac outlets and other cards with death triggers.  Add in Marchesa and you can sacrifice creatures that ETB with +1/+1 counters on each player's turn, bringing them back at the end as untapped blockers for the next turn, then rinse and repeat.  Any creatures that don't naturally put +1/+1 counters on themselves will have to attack and use dethrone to gain Marchesa's recursion protection, but that's not too big of an issue (plus we have a few other ways to put +1/+1 counters on creatures at instant speed).  Having your creatures ETB with +1/+1 counters also alleviates your need to abuse dethrone and primarily attack the player with the most life, which will change the dynamic of how everyone else reacts to your shenanigans.  And being able to attack anyone you want lets you dictate your own game plan better.

The biggest question of a build like this is where to put your money...?  First, it's important to recognize how cheap this deck can be built with high synergy cards that do a lot in tandem with Marchesa, but are very cheap to buy.  That being said, Marchesa is tri-color, and the better the lands, the faster the deck, so I'm thinking that's my focus: build cheap and efficient everywhere else and invest in the lands.  It already has enough good ramp and draw to explode cards out, so a solid mana base that can ETB untapped could make it a lot more competitive.  If you wanted, you could certainly go cheaper on lands and swap a few cards into other slots that cost more, and help the deck more.  It's up to you.

(Keeping it under $100 over time might prove to be an interesting task... but this list will get updated as I swap out cards in an attempt to keep it cheap.)

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One thing I dig is the synergy between Marchesa and the graft mechanic. As creatures ETB, move +1/+1 counters from, say, Novijen Sages onto those creatures so they can be revived from a sacrifice, leaving one counter on the Sages. At the end of the second main phase of every turn, you sacrifice each of these creatures to a sac outlet, then when they return at the beginning of that end step, have Novijen Sages ETB first, then each of the next three creatures gets a counter from it. The next turn you do the same thing. On each player's turn, you get death/ETB triggers and the creatures enter protected by the +1/+1 counters and Marchesa. Cytoplast Manipulator, Helium Squirter and Vigean Graftmage are the other graft cards in grixis. All four have high value in the Marchesa deck.

Jar of Eyeballs is sneaky good in here, primarily because it lets you put all the cards you looked at on the bottom of your library in any order.  Say you have 80 cards left in your library... you need to have creatures you control die 40 times, which sounds like a lot, but with four players if you sacrifice five creatures on each player's turn (which isn't a far-fetched reality), after two complete rounds of turns you'll have eighty counters on the Jar.  Four crits a turn will get you there in three rounds of turns.  Then you're reorganizing your whole library.  And you aren't sacrificing the Jar, so you can potentially use it again if someone forces you to shuffle your library.