http://mtgbudgetbro.blogspot.ca/2013/04/budget-rakdos-elemental-combo.html

Let's talk about the core of this deck. Fortunately all the pieces are inexpensive enough that we can afford to leave the deck's core untouched. This core consists of the creatures Flamekin Harbinger, Kiln Fiend and Nivmagus Elemental. Additionally, we will use 12 free spells: Gitaxian Probe, Gut Shot and Mutagenic Growth. The last core pieces are Apostle's Blessing, Assault Strobe, Ground Rift and Tainted Strike. The only change we will make to Thompson's core is to include a full playset of Assault Probes, rather than just two. While Flamekin Harbinger is expensive at $1.50 each, the difference between 8 and 10 elementals is huge. I agree with Thompson in that four copies of the Harbinger are a bit much, but two greatly increase the deck's consistency.

A few notes on playing this deck. You should do everything in your power to have at least one Nivmagus Elemental or Kiln Fiend on the board. Don't be afraid to mulligan if you have to. Don't be afraid to play your Gitaxian Probe on turn one or two if you need an elemental or a land. Before you go off, try to cast a Gitaxian Probe or Duress if able. The perfect information provided by the cards will ensure you know if it's safe or if you need to hold back a bit to save your creatures. However, if you have a Nivmagus Elemental, then it may still be worth it to exile the spells. You may exile Ground Rift's copies with Nivmagus Elemental to place extra +1/+1 counters on your guy. The copies do not trigger Kiln Fiend's +3/+0 ability however.