The theme of Gitrog decks is discard, dredge, and landfall.
Gitrog Coming in at 5 mana, The Gitrog Monster is no lightweight. In order to drop him in a timely fashion we play an abundant number of Fast Mana Pieces.
Discard Outlet: Skirge Familiar is the discard outlet that most easily wins us the game, but it's 5cmc and we can technically go off with other discard outlets and put in a little extra work.
Dredge: Nothing replaces Dakmor Salvage. BUT... Any "Dredge" card can help us get to Dakmor Salvage. Gitrog + Discard Outlet + Dredge X card = Mill X cards, if you hit a land, repeat. As long as we keep hitting lands, we get to keep repeating until we hit Dakmor Salvage and can start the Proper combo in full.
Tutors : Getting everything together takes effort, and Tutors give us the consistency we need. Tutors will fall into three different categories -- Land Tutors, Creature Tutors and Everything Tutors. Jarad's Orders on 5 into Gitrog on 6 -> Cast Imp and go off on the same turn.
By the way, you'll need 1 or 2 Eldrazi Titans to insure you don't mill out. I run 2 for redundancy in case something happens to the first. Last thing you need is for your only shuffle effect to get exiled out.
But we're not running without opponents. Solitaire is all fine and nice for seeing how quick a deck could work, but it never shows how quick a deck actually does work. We need a way to stop our opponents from doing opponent things that mess with us.
Anti-Graveyard Hate
Getting rid of Graveyard Hate is a tough thing. There are 3 main contenders that'll Hate us out:
Anafenza, the Foremost -- Rest in Peace -- Leyline of the Void
We want to play answers that'll hit all 3 preferably and if not, at least 2 out of the three. Abrupt Decay is on color, uncounterable, and drops Anafenza and RiP. Nature's Claim is cheap, efficient, and hits 2. Krosan Grip also hits 2, and is uncounterable to boot.
Sudden Spoiling only hits Anafenza, but I include it due to the mass of Laboratory Maniac I face in my meta.
Beast Within is a possibility, and one that hits all 3 issues. I don't include it, but you should consider it.
4 Anti-Graveyard Hate Cards
Anti-Counterspells
Autumn's Veil and City of Solitude protect us from counterspells on our turn. If your meta is full of "Draw/Go" style control decks, you'll want to include these, and maybe others.
2 Anti-Counterspells Cards
Recursion
You're going to lose cards. Having ways of bringing things back is mandatory.
[Riftsweeper] is one of our most important recursion pieces. Not because it brings things back from the Graveyard, but because it brings things back from Exile. While you're a little resilient in that you can run without most given pieces, it's better to have Riftsweeper than not.
Eternal Witness and Skullwinder help defend while recurring a card. Skullwinder is typically skipped over, but I like the Deathtouch "rattlesnake" aspect and I'll typically be able to chose and opponent who gains the least benefit or presents the least threat (or greatest political advantage). Regrowth plays the same role sans creature on board.
Crucible of Worlds and Ramunap Excavator should be included in the Recursion category, even though they only recur lands... But oh how they recur lands! Playing the land you just sac'd to Gitrog means you've lost nothing. They are excellent additions.
Splendid Reclamation is another Land-recursion card, but it does so much work that we can't help but include it. With Squandered Resources, we can sac lands to Resources (Drawing cards while doing so), cast Splendid Reclamation with the mana gained bringing them all back. Then sac them all again to generate even more mana and draws.
Necromancy recurs a creature and is excellent for starting your combo at instant speed. Nothing says "I win at all Magic, Forever" like comboing out on someone else's turn.
8 Recursion Cards
With 4 cards left, we get into the oddities from here.
Sylvan Library helps propel your game into the cards you need to draw. Often beneficial to take the 8 life just to get the cards out of the way.
Toxic Deluge is a cheap, efficient board wipe that we can drop down in necessary situations. We don't care about the first 39 points of our life total, so paying X life is nothing.
Raven's Crime is here to tear apart opponent's hands mid-combo. There will be a few things that can undo our combo mid-way, and Raven's Crime forces their hands to either cast the spell or ditch them.
Constant Mists keeps aggressive attacking strategies at bay almost indefinitely. There are a few combos that end with combat steps (Kiki Jikki for instance), and Constant Mists will shut those down.