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There is 0 reason to avoid Innistrad Block.  You lose Pillar of Flame , Stromkirk Noble , Stonewright , Hellrider and Falkenrath Aristocrat .  Those cards are all good until October.

For lands, 4 Dragonskull Summit at the minimum.  If you can get 4 Blood Crypt in addition you'll be well on your way to having a solid mana base.  Depending on your build, you may only need 2 Guildgates.

-3 Horror, he's situatuionally good, which makes him a bad creature.
-3 Imps, to high a mana cost for Aggro.
-2 Hellstead, still too high costed for Aggro.
-2 Guildmage, it's alright in draft, but in Constructed it's a little lack luster.
-1 Instinct, too high a cost for the effect, and you only need to draw 1.
+4 Ash Zealot , she's a staple Red Aggro creature, and isn't hard to hit with the current non-basics.
+3 Deathrite Shaman , a sudo- Grim Lavamancer
+4 Nivmagus Elemental , 1-drops are good, and since you don't want Innistrad Block, I think he's the next best option.

More Dreadbore, less Spree would be good.  And I'm not a fan of Stab Wound, Giant or Thug.

I'd also go:
-4 Stab Wound
-3 Giant
-3 Thug
+4 Annihilating Fire
+2 Desecration Demon
+4 Rakdos Shred-Freak or Gore-House Chainwalker

I think that's the best I can do until we know all of Gatecrash, or you suddenly change your mind and allow for Innistrad Block.
 

The update looks like a pretty good budget Rakdos deck. Stab Wound is pretty awful though. I'd ditch it for, well, pick something.

Kindled Fury is probably another one that should go.

You probably want to stick with cheap stuff - mana-wise as well as $-wise. Some thoughts include;

Ultimate Price
Crimson Muckwader

There is a crap load of stuff inInnistrad block. I can see not buying rares that aren't long for this format, but you can probably get commons for free. A few thoughts here are:
Pillar of Flame
Bump in the Night
Brimstone Volley