Scepter of Celebration will provide trample and a ton of bodies. The Reaver Cleaver does the same but spits out treasures.

Board wide damage effects seem pretty good with your Commander, Pestilence, Pyrohemia, Chain Reaction and Blasphemous Act all jump out as good enough cards. Mandate of Abaddon is probably well beyond good if Kresh is at all beefy, he'll suddenly be even bigger on an empty board if all goes well. As long as your Commander has at least 4 toughness Ezuri's Predation would be hilarious, even if a bunch of 4/4s bite the bullet your Commander just gets bigger.

Rite of the Raging Storm seems almost unholy with your Commander, I normally love this card but here you are going to be farming 5 power creatures over and over, and they're never attacking you.

They're both small and random, but Temur Battle Rage and Tainted Strike can both turn your Commander into a 1 shot fairly easily.

If your Commander is fairly big then Return of the Wildspeaker, Rishkar's Expertise, Soul's Majesty, Momentous Fall (also good if your Commander is going to die, as is Greater Good), Grothama, All-Devouring, and Mask of Griselbrand can all draw you a decent number of cards. Overwhelming Stampede and Fungal Sprouting both seem very good with your Commander.

I like Fight effects if I suspect I'll have the biggest body on the board, Ulvenwald Tracker, Domri, Anarch of Bolas, Kogla, the Titan Ape, and Thorn Mammoth are pretty good sources you can repeat.

Thunderfoot Baloth, Siege Behemoth, Kamahl, Heart of Krosa, Blossoming Bogbeast, and Goreclaw, Terror of Qal Sisma are decent sources of Trample that are stapled to a body, and they're all fairly budget. Keep an eye out incase Pathbreaker Ibex goes down in price, that's a very good effect with your Commander. Just a heads up, but if you run lots of sources of Trample for your Commander, then anything that provides Deathtouch looks a ton better, with Deathtouch you just deal 1 damage per creature and Trample over the rest. Bow of Nylea, Saryth, the Viper's Fang, and Ohran Frostfang are all very good sources afaik, there are others kicking around if you look!