TACTICS:
Discard creatures using Llanowar Mentor, Lotleth Troll, and Raven's Crime. Archfiend of Ifnir can be cycled.
Vigor Mortis, Zombify, Doomed Necromancer, and Moldgraf Monstrosity are used to play creatures from the graveyard.
Use removal (Beast Within/Reanimate Ashen Rider) to deal with threats. If you're drawing excess lands, cast Raven's Crime on your opponent for added advantage.
NOTES [ARCHFIEND OF IFNIR]:
Archfiend of Ifnir is not to be underestimated. Its ability allows you to very easily wipe out all of your opponents' weaker creatures and cripple their stronger ones. The ability works even if your opponents creatures are indestructible, have shroud/hexproof, or have protection from colors/creatures.
Since the Archfiend's CMC is 5, it is possible to cast it mid-game, so you might not need to cycle/discard and then reanimate it.
Remember, Archfiend's ability triggers every time you discard a card. It will trigger when you activate Llanowar Mentor's ability, when you activate Lotleth Troll's ability, when you cycle another Archfiend, when you use Raven's Crime to force yourself to discard a card, and when you cast Raven's Crime via Retrace.
NOTES [RAVEN'S CRIME]:
Raven's Crime can be used to make you or your opponent discard. If you find yourself drawing too many lands, you can always make use of its Retrace function.
NOTES [MOLDGRAF MONSTROSITY]:
If you have multiple creatures in your graveyard and don't know which one to reanimate, prioritize Moldgraf Monstrosity. You can continuously attack with Moldgraf Monstrosity in the hopes that it will die, so you can then reanimate two other creatures.
If you wish, you can also use Beast Within to destroy your own Moldgraf Monstrosity. This will get you a 3/3 beast token while also triggering Moldgraf Monstrosity's ability. I've done it while play-testing , and it works quite well.
NOTES [ASHEN RIDER]:
Ashen Rider can act as removal. Reanimate it to exile a permanent. If someone attempts to deal with it in a way that does not cause it to die, you can always use Beast Within on it, as Beast Within is an instant. You will then get to exile another permanent and gain a 3/3 Beast token.
REVISIONS:
As is, this is a budget deck. If I were to remove the budget restriction, I would likely add Abrupt Decay or Maelstrom Pulse as removal, instead of Putrefy and Beast Within.