each one is going to depend on several factors, ie, your body size and tolerance, the types (strains) of each plant you listed etc...
but in general, kratom for me as a person with little opiate tolerance becomes enjoyable starting at the 4-5 gr mark. I am a fan of the super green and super indo varieties. People with tolerances orwho happen to be somehwat hardheaded with their dosages need up to 20 gr though. Personally that amount would send me into a vomit session, but everyone is different.
blue lilly can be enjoyed in a couple different ways. Smoking and making a tea are probably the most common. I enjoy both ways and often will combine smoking with drinking the tea to achieve greater effects. Blue lily is a bit more subtle than kratom though. Some people have trouble experiencing the effects with blue lilly due to this. A way around that might be to work with an extract. I've sampled many of them, from 5x-100x, as well as having made my own extract using everclear. To date the 100x and my own extract were the most enjoyable, with the homemade extract actually rivaling decent grade middies for weed in effects. The one thing about blue lily that I love the most tho is its ability to combine and potentiate other things. People use it to good effect to add some kick to their opiate/kratom experiences, but my favorite thing to combine it with is good old weed. It really makes weed stronger and the effects become so much like how my first great weed experiences were...more magical, more cevs, a nice little relaxed body feeling...good stuff. Lastly, blue lily is amazing when steeped in wine for about 1-2 weeks and then filtered out and drunk. The blue lily synergizes with the wine and brings out what I call wine's psychedelic side. And again, add some weed to that experience and it is like the holy trinity of getting stunk and droned.
wild dagga is definitely active, and I personally enjoy it, but it is prob the most subtle of the three you listed. Depending on what part of the plant you have, the potency varies. In my experience the best part of the plant to work with is the red or orange flowers. The buzz they give me is nice, short lived, and somewhat reminiscent of a cross between weed and tobacco. I like a nice fat joint of it from time to time, and it mixes well as a joint with the blue lily too. People make tea out of this one too, but in my opinion it tastes foul. People also use the leaves from this plant to smoke and make tea, but in my experience the leaves taste really bad and make working with them a lot less enjoyable than using the flower heads.
that's all i can think of before my coffee this morning...
good luck
