syrian rue is not just cheap and easy to get (middle eastern shops often have esphand for incense or dye purposes) but it's amazingly potent. 4g (less than one tablespoon) of average seeds is usually plenty powerful enough for ayahuasca or mush-huasca.
also btw, ayahuasca the term itself refers more to the brew of b. caapi vine and p. viridis leaf. sticklers like teotzlcatl will tell you that anything containing p. harmala and/or m. hostilis should be called 'anahuasca' (analog huasca), 'mimosahuasca', or 'pharmahuasca' (in the case of moclobemide or other pharmaceutical MAOI agents).
personally i'm a fan of psilohuasca (syrian rue + psilocybin mushrooms) as it is one HELL of a ride. 15 minutes after ingesting p. harmala seeds, i took an unmeasured quantity (probably 4-5g) of psilocybe cyanescens mushroom. not ten minutes following that, the walls began to breathe. in another ten minutes i was curled in the fetal position crying for the universe to please stop spinning i want to get off. i was completely lost in my own mind for the next few hours, and the come-down was amazingly abrupt. one moment i was surfing through time, and the next moment i opened my eyes and was 98% sober save for being shaken to my very core.