Hey,
Prismatic Omen feels like a little overkill for the deck (especially for the budget) but if you have one, its great.
Then I would clean up the land base. My golden Rule here: "if it always enters tapped, it needs to have a significant effect". We can argue about the Scry lands (even if I don't think the scry 1 is THAT important for your deck) but everything worse should go. Since you're playing green, colorfixing shouldn't be a that big deal.
Exotic Orchard also helps alot.
I've just checked my
xantcha deck for some ideas, this is what I have found:
Maddening Imp (cleans up creatures with summoning sickness)
Mass Hysteria (haste for all, let them beat themself earlier)
Crown of Doom (another option to let them beat themself, let them play hot potato)
Backlash (in case someone puts a real fatty on the board)
Repercussion (damage for blocking creatures)
Curtains' Call (potent multiplayer removal)
Since you produce alot of tokens,
Diabolic Intent could be interesting. Same cmc but a little more affordable than
Diabolic Tutor.
Tempting Licid could also be interesting for some nasty combat tricks (force your opponents to block).