Cards to Consider
Evolutionary Leap - An excellent sac outlet that provides more card advantage, this would've gone in already had I had a copy.
Chandra, Flamecaller - Her +1 puts two Elemental tokens onto the field, which, provided we have a sac outlet, can be cashed in for two free Bolts from Omnath. Plus, her 0 ability can be useful if our hand gets stalled.
Ulasht, the Hate Seed - In an ideal world, we G-Wave, have loads of creatures and lands hitting the field (creating loads more tokens), then Ulasht hits as something ridiculously large and we use Ulasht's activated ability to turn him into a pseudo Fireball.
Spearbreaker Behemoth - We've got lots of stuff with 5 or more power.
Gruul Ragebeast - Each Landfall trigger becomes removal on top of a token.
Second Harvest - Doubling the bodies on the field at instant speed sounds pretty nice.
Rampaging Baloths - He does part of what Omnath does, but for 4/4 Beasts.
Nylea, God of the Hunt - Trample is a great thing to have.
Pathbreaker Ibex - Works pretty well when he's attacking alongside a swarm of 5/5s.