I'm looking to build up up ethnobotnical garden and would love to have some acacia and syrian rue growing, at the moment it's all cactus, I am struggling to find info on the seed yield a rue plant gives, anyone who grows rue have any input regarding seed harvesting, time, plants, yields..thank you!

Definitely!
Depending on where you're living, it could be quite a challenge (I'm struggling at the moment, but I've managed to get two seedlings established enough that they might be able to survive the winter, fingers crossed), but I'm sure that the reward would be worth it. Either way, they're pretty low-maintenance plants so I reckon it would be worth it anyways.

I've found acacias can also be a real pain to grow, at least in my climate (although this probably only applies to acacia acuminata). At the moment I've been trying to track down some acacia mucronata subsp. longifolia seeds, as being Victorian natives, they might stand a better chance. I would have a shot at acacias as well though, even just seeing the adorable little acacias grow their first phyllodes definitely makes growing them worth it

Syrian rue is worth growing. Its difficult to start but once they have established and begin vegetating they're practically self-reliant plants and branch out fairly quickly, but make sure to leave the soil mostly dry and sandy, and water thoroughly a couple times per week and remove all of the runoff. Rue can effectively handle drought but not for very long, and any over-watering could easily drown Syrian rue. Once a rue plant begins to die it dies sooner rather then later, so always make sure that once a branch dies off that the plant is healthy enough to stimulate fresh growth.

Also, expect loss during the germination period. I started with roughly thirty seeds and only ended up with about seven seedlings. Once rue takes off it can get big and bushy.