Hm. I used to play Rakdos a lot. I would personally recommend Master of Cru. as it's a very good card. Definitely add 2 Stormbreath Dragons in there.
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I would mainboard 4x Fanatic of Mogis. Maybe some Chandra's Phoenix. They are really useful for Red Deck's. If you have extra money, Purphoros and his hammer would work very well.