I think:

Chandra, Pyromaster would fit in here..... +1 loyalty is nice with Madcap Skills ...

Boros Reckoner is just a thought..... always nice creature with Red mana available..

Coordinated Assault was another thought with Madcap Skills ??.... Or all around with your "haste" creatures eventually... even with the 2R tap ability of "hammer" thats a haste 4/3 first strike possible golem attacking...

Good luck fellow Rakdos friend... or feind!

I really like this and had a construct that was similar. I like the combo of Dying Wish on the Hellhole Flailer sac em for double damage and gain some life in the process.

It's a cool combo, but I don't think the deck can afford having a card just for that. Thank you, anyway.

http://tappedout.net/mtg-decks/turn-4-win-rakdos-aggro/ this is my build it works a wee bit better but it is unbudget

Maybe consider Bile Blight against the token and weenie decks. It is also an amazing card in just about any situation. Exava, Rakdos Blood Witch is a great card...but possibly not in this deck, she is the only card you run with counters. In place of her consider Chandra's Phoenix or Ash Zealot . Both of these are quicker plays and more versatile creatures for your deck. Especially the Phoenix. You may consider Skullcrack over Ultimate Price as well, in the current meta, lifelink and cards like Ajani, Mentor of Heroes are popular. Skullcrack shuts them down.