So the power of the commander is heavily based on taking life from the opponent and then, if you do so, lowering the mana cost for creatures by each life lost. So, I would put in mainly, if not ONLY black and red creatures that lower the life of the opponent. Don't be discouraged by mana cost because the more life you can take, the cheaper it will be. I would take out many of the instants, artifacts, sorceries and enchantments since they don't pair well with your commanders abilities. Also, I would limit your planeswalkers to either Sorin, Chandra, or both if you'd like. they are the only ones that you can really dominate with this deck. Lightning bolt, Kolaghan's, Palace siege, Exsanguinate I'd keep for non creatures, maybe add a few more that are cheap and focus only on life loss like Shamble Back and Stab Wound , with stab wound being a great addition to this deck if you compare what it does to your commanders affects. Overall, this could be a great deck, but you want to have most if not almost all the cards having some sort of power where the opponent loses life in some way. Creatures being the majority since they cost less and can be virtually free to play. Hope you have enough cards to make this work. If not, there are plenty of cheap cards to boost this deck with and still be awesome

Gray Merchant of Asphodel is pretty awesome with Rakdos.

Actually austinjsp this list looks pretty solid, and how is Shamble Back life loss for the opponent? Jw

Shana42 Nice non-creature burn package and the creatures seem to be on "point" when it come to Rakdos' battle plan. If anything I think you would want something like Balefire Dragon, who can act as a one sided boardwipe to help quell your enemies forces. Also creatures like Sin Prodder are very useful because either you get an extra card at your Upkeep or an opponent just set themselves up for damage that will help lower the CMCs of your creatures whilst the Lord Rakdos is out and about on the battlefield.

One Enchantment I suggest is Manabarbs. It looks "eh" but it forces Control decks to either answer it or take ridiculous amounts of damage over time that, while facing off against this deck, will cost them the game in the long run. I personally love watching the result of this cards ability because if someone just wasted or has no Enchantment hate it rules the game for a while. More Burn enchantments/spells might be of use depending on your personal preference but like I said, solid list.

These are just my personal opinions off the top of my head from playing Rakdos, Lord of Riots before. If you found anything I said helpful I do have more suggestions and combos for Rakdos that I have written down somewhere that I used in my old list. Other than that, +1 from this guy!

Maybe add a couple tutors, such as Diabolic Tutor and Rune-Scarred Demon

Pestilence is like another Pyrohemia and seems like a good addition.

Faceless_Being oops Shamble back is wrong I was mistaken, but I just mean if I was building this deck I would try to mainly focus on cards that either have trample and high power, or which deal damage directly to player, those being favored. Many black cards also have a feature where you gain life when your opponent loses life and I'd add some of those too. Also, the planeswalkers, while being good cards, aren't necessary at all besides the 2 I mentioned above I mean keep them in if you'd like but I mean... To even cast the commander the opponent must lose life, and while there are a few great cards in this Chandra, Fire of Kaladesh  ^Flip , there are only a handful of cards that have trample or that actually lower opponents' life. Kothophed, Soul Hoarder can be a great card in some decks, but this deck isn't a draw deck and it does the opposite of what is wanted. I think it's the start to an amazingly powerful build with potentially infinite mana being fueled by opponents life loss, but some of the cards need to be changed out for cards that would work better in this case

Exquisite Blood being one, which you already have I see nice

thanks everyone I really appreciate the help <3