Cult of Rakdos

With Commander being primarily a group format, I'd swap out at least some of the spells that deal damage to "target player" with something that deals damage to "each opponent". There are quite a few red creatures that tap to deal 1 damage to each opponent. That way, the more opponents you have, the cheaper your creature spells get with each ping.

For example, Lobber Crew taps to do one damage to each opponent and when you cast a multicolored spell, you can untap Lobber Crew. Let's say you have 3 opponents. You tap Lobber Crew to deal 1 damage to each of them which reduces your creature spells by 3 mana for that turn. You play a B/R creature with CMC 5 or less for 2 mana which allows you to untap Lobber Crew. Tap it to deal 1 damage to each opponent again which then allows you to play a creature with a CMC of 8 or less for 2 mana. As long as you keep playing multicolored creatures, you'd be able to play bigger and bigger creatures for 2 mana.

Along with Lobber Crew, there's also Lightning-Rig Crew (untaps when you play a Pirate spell), Nettle Drone (untaps when you play a colorless spell), and Thermo-Alchemist (untaps when you play an instant or sorcery).

With all that available, you could also get some high-cost Eldrazi into play for cheap or even for free. If you had some creatures with X in their cost, you could pump a lot into X for very little mana. "Grenzo, Dungeon Warden", Endless One, Balduvian Hydra, Lightning Serpent, "Maga, Traitor to Mortals" (which could also further decrease creature spell costs). If you play, "Maga, Traitor to Mortals" before your other X-cost creatures, you could make those other X-cost creatures ridiculously big. You could also play a Gray Merchant of Asphodel or Fanatic of Mogis before the X-cost creatures to give you a huge boost if you have a lot of black or red mana symbols on permanents you control.