I second the Lemon Balm, i highly recommend it to pretty much everyone. It cleans up how the Rue feels, and smooths out the intense oral DMT/Acacia/Mimosa or even the less intense Psilocin come up. It helps reduce intensity during the come up, relax/ease the mind, and helps make things more user friendly/navigable without feeling overwhelmed. I personally use and recommend 3 to 4.5 grams of dried Lemon Balm leaf made into tea (steeped in a cup of fresh hot water for about 15 to 20 minutes, then filtered/strained off and the tea sweetened and consumed), 4 to 4.5 grams and there's little to no intensity, 3 grams the intensity is reduced but still there a bit.
Cannabis can be good, but after using it with this stuff for most of my experimentation, i've come to the realization that if i'm going to smoke Cannabis, then to smoke it after the come up and everything has kicked in, otherwise it can amplify the paranoia and anxiety, and increase the intensity.
Tobacco can be good too, personally i find Tobacco helps me talk in tongues with a good dose of Rue and either Acacia/Mimosa or mushrooms/4-ACO-DMT, with or without Lemon Balm, Cannabis may contribute, i'm not sure, but i'm pretty sure it's mainly to do with the Tobacco.
As far as anti-nausea effects go, Limonene is probably your best bet, at least ime so far. I've personally tried Ginger root tea, Ginger EO, Zofran, and Peppermint, and none of them really helped with the purgative effects, but Limonene seems to. 5-HT3 antagonism doesn't seem to do much for the purgative effects, but Limonene seems to help either by agonizing the 5-HT1A receptor which apparently inhibits a receptor called NK1, or because it seems to help get digestion going. Both Zofran, and Ginger, seemed to alter the medicine in a very undesirable way ime, but i could've perhaps used too much Zofran, and too much Ginger. Also some sort of anti-cholinergic should help with the motion sickness and dizziness, but i'm not sure as i haven't yet tried it, though be careful with anti-cholinergics, and be careful with something like Benadryl which is metabolized by CYP2D6 which Harmalas potently inhibit, thus requiring a much lower dosage of CYP2D6 substrates, same for CYP1A2 substrates, so that would also affect Zofran since it's metabolized by CYP1A2 and CYP2D6 so imo if you try Zofran, try no more than 2mgs or less.