MTG Salvation

3 lands, one or two ramp. That's about how much you need to start a good game. It doesn't really matter what the other 2 or 3 cards are as long as you have those cards. Cards to avoid mulling for more lands/ramp:
Token Doublers
Mass Boosters
Game Enders

This is your set-up time. Just try to get Prossh out as soon as possible. If you have Purphoros, God of the Forge, Endrek Sahr, Master Breeder, Strionic Resonator, and/or Parallel Lives, then it is worth taking an extra turn or two to get them all out before playing Prossh. WARNING: Don't look too scary if you don't have the resources to actually finish the game. You don't want to be the target if you don't deserve it. If someone else is being an obvious target, let everyone worry about that while you set up for your alpha-strike. If you can make your game- winning play turn 8 (I guess that's the early game) then by all means do it. Don't set up for later if you have an opportunity now. Once I had Parallel Lives and Purphoros, God of the Forge out, then played Army of the Damned, hitting everyone for 52 damage. This was turn 7. I felt kinda like a jerk, but it does show the power of this deck.

This is where you should win the game. Just as everyone is starting to really use their deck to make things happen, you win. If you are playing against blue, you might have to wait for them to tap out or tutor for a backup plan (an extra mass booster, for instance). If you get thwarted once, by board wipe or otherwise, it will probably look like you've run out of fuel, but you will probably be able to go for another one in a couple turns. Do that if you can, but if you can't then back up and start playing tactically. You don't want to lose because everybody ganged up on you because you seem like the biggest threat. You will now obviously be a major player in the game, and you will be attacked if possible. To prevent this, set up some defense, and move on to the Late Game.

This is where it gets tricky. A game with Prossh rarely lasts this long, either you win in the beginning or get kicked out of the game in the middle. (the second doesn't happen often) If you are in this situation, I can't give much advice, because it starts to really depend on what kind of decks your playing. You really have to start interacting with the rest of the game, and letting other people look scary. Chances are no one will set up a strong enough defense to hold off your alpha strike. Your big moment will be more complicated, and it might not even come at all. Maybe you will just wait, watch a couple people get killed, and then knockout the last couple with Prossh commander damage. Usually though, you will be able to pull one more alpha strike, and it will probably be better than the last ones. Remember, you will pretty much always have another way to win, so always

CREATURES:
Eternal Witness: Recursion on legs, pretty strait-forward.
Solemn Simulacrum: Great ramp and draw. Would be silly not to play it, especially in a sac deck.
Ogre Battledriver: Good haste enabler, as it boosts you kobolds too. Sometimes I add Food Chain (when my playgroup plays infinites) and this gives me an easy win with it. Otherwise it is just a good booster.
Anger: Great for haste; unless it gets exiled, it is guaranteed. Prossh can eat him up nicely.
Jarad, Golgari Lich Lord: I see this in Prossh deck less often, but it is really a must include. If you have Prossh and 15 creatures, sac them all to Prossh and sac him: 20 damage to all your opponents. Usually a later-game wincon or a finisher if your alpha strike wasn't quite big enough. It's also really good with Fatal Frenzy, can kill the table in as early as turn 10 with the right set up.
Marton Stromagald: A very powerful way to win. Basically the same as Craterhoof Behemoth if you have haste. His 1/1 body is the only downside.
Purphoros, God of the Forge: This is an obvious choice, it can kill the table very quickly. Watch out though; it makes you quite a target.
Oracle of Mul Daya: Really helps you to dump your hand and win extra fast. Great ramp, especially with 38 lands.
Endrek Sahr, Master Breeder: This is an incredible card or Prossh. It doesn't see play as much as it should. It basically doubles your tokens, but it makes can make a token producer out of any creature.
Dragon Broodmother: A great token producer. Can make a lot of little flyers or a few big ones, depending on your situation.
Dragonlair Spider: Another good token maker, usually ends up making more tokens than Broodmother.
Chancellor of the Forge: One of the 2 standard Tooth and Nail targets. Gives me hasty tokens that can smash face when boosted with Craterhoof Behemoth.
Rune-Scarred Demon: Another good Tooth and Nail target, good tutor with a good solid 6/6 body.
Sheoldred, Whispering One: Thinking about switching this for Whip of Erebos. Both are good, but the Whip is a little more political, plus having a life gain option could come in handy.
Butcher of Malakir: Powerful card. Lets you basically do a board wipe and make everybody hesitate before playing creatures. Definitely makes you public enemy #1.
Creterhoof Behemoth: The prime win condition in the deck. No more explanation needed.

ARTIFACTS:
Sol Ring: Duh. Really nice to get a turn 3 or 4 Prossh.
Skullclamp: Goes in any sac deck. Pay one mana, lose one kobold, draw 2 cards? Yes, please.
Blade of the Bloodchief: Great cad for Prossh, blows him up to scary proportions.
Lightning Greaves: Prossh doesn't need a lot of protection, but it's good to have one just in case.
Strionic Resonator: Token Doubler! Also works wonders with: Eternal Witness, Solemn Simulacrum, Marton Stromgald, Endrek Sahr, Master Breeder, Chancellor of the Forge, Rune-Scarred Demon, Sheoldred, Whispering One, and Craterhoof Behemoth.
Gruul Signet, Golgari Signet, Rakdos Signet: Great with Sol Ring, and for filtering colorless mana. 5 mana turn two? Yes, please.
Darksteel Ingot: Indestructible ramp.
Gilded Lotus: Really good accel.

ENCHANTMENTS:
Concordant Crossroads: Pretty good haste enabler. Could be replaced with Fires of Yavimaya, But I personally like the option of getting really cheap haste when I need it, despite its drawbacks.
Goblin Bombardment: Good sac outlet, Combos with Food Chain when I use it, gives me an alternate outlet to Prossh.
Fervor: More Haste!
Shared Animosity: Great booster, can get my creatures really big if I have a doubler.
Fecundity: Great card draw, plus a little group hug.
Beastmaster Ascension: very good beefer-upper, makes all my creatures frighteningly huge.
Parralell Lives: Token Doubler, duh.
Primal Vigor: Doubling Season is better, but I don't currently want to invest in such an expensive single. Watch out with playing this against another token or +1/+1 deck. Prossh is just about as hardcore as it gets, but something like Rhys the Redeemed might be able to better use it.
Vicious Shadows: A great card that can kill the table if you have enough creatures and an opponent has enough cards. Pretty much prevent wipes.

PLANESWALKER:
Garruk, Primal Hunter: Great card draw, plus an amazing big ability.

INSTANT:
Tainted Strike: Allows for an easy kill with Prossh.
Go for the Throat, Terminate: Good instant creature removal.
Fatal Frenzy: Great way to easily kill someone, also for killing someone with Jarad, Golgari Lich Lord. Yes, Berserkis better, but it is quite above budget for me.
Beast Within: Green staple removal.
Putrefy: Good removal with options.
Savage Beating: I don't know for sure if this is better that Triumph of the Hordes or not. Any feedback on that matter would be appreciated.
Hit // Run: Great instant-speed booster with removal option.
Starstorm: My primary board wipe. Blasphemous Act is more efficient, but it is very good to be able to wipe at instant speed.

SORCERIES:
Cultivate: Great ramp.
Saproling Symbiosis: Great token maker, especially with the added Instant-speed flexibility.
Jarad's Orders: Good tutor that can get Anger and some other creature, giving me haste an a creature for 4 mana. Good deal.
Diabolic Tutor: Duh. Tutor.
Increasing Ambition: Good tutor plus flashback. Belongs an most decks just as much as Demonic Tutor.
Demonic Collusion: More budget tutoring.
Overwhelming Stampede: Great mass booster, doubles Prossh's power or boost's all my creatures.
Beseech the Queen: Budget Tutor, the first to be replaced by better ones.
Boundless Realms: Great way to get all the mana I need. Is an underplayed card in my opinion.
Tooth and Nail: Amazing card, green staple. Usually means I win with Chancellor of the Forge and Craterhoof Behemoth, but is also more flexible.
Army of the Damned: The most efficient token producer in the deck. Due to the tapped status of the zombies, I usually try to win with a doubler and Purphoros or Vicious Shadows and Prossh/Bombardment.
Warp World: Such a fun card to play. With the high permanent count and the tokens, I should be better off than everybody else. This is more for the awesomeness than the win, but it is especially good in this deck.
Innsurrection: Take everybody's creatures, kill a couple people (or everybody if I have a mass booster), then kill all the creatures via sac outlet. Pretty obvious why it's worth a slot.
Plague Wind: Everybody's creatures die. Pretty strait-forward.
Tempt with Vengeance: Great hasty token producer.
Diabolic Revelation: Great tutor for lots of cards.

Doubling Season: Just don't have it yet, so Primal Vigor will have to do.
Ashnod's Altar: Don't have the room or the reason. This deck just isn't really made for sacrificing creatures all the time. It needs the creatures to kill people. It has the option to sac them, but it can't run too many.
Mycoloth: I love this card. It doubles my tokens every upkeep! Isn't that great! Not exactly. It's problem is that it is too vulnerable. Who in their right mind would actually let it live to the next upkeep. If I play it, I will accomplish nothing but losing all my creatures and wasting my turn, and forcing someone to kill it. It just isn't worth the risk.
Both Xenagoses: I just don't have them yet, Xenagos, God of Revels will replace Fatal Frenzy, and Xenagos, the Reveler will replace most likely Solemn Simulacrum.
Avenger of Zendikar: I can't wait until I get a copy of this, play it, then play a Boundless Realms. That is my dream play. But until then, I will settle for Chancellor of the Forge.