Greetings, friend! I'm also new here but like you am from Australia. You say that mushrooms are not readily available to you...how do you figure by this? NSW hosts some of the largest Psilocybe subaeruginosa patches I've ever come across. They're probably most naturalised there than anywhere else, actually. The season also just started; check out the NSW thread on Shroomery's Mushroom Hunting and Identification section to get some saliva flowing.

As far as I know your acacia plant will take years before it is able to withstand bark harvesting. You'd have better luck looking through the 'trying to improve Acacia information' thread on here and finding out which active acacias grow abundantly in your area. Of course, growing your own is still a very rewarding and sustainable experience, so do not be put off by it! My humble suggestion is that you try mushrooms before DMT; not because DMT is some dangerous super-drug, but because you will find mushrooms more easily available and slightly more forgiving to a psychedelically naive mind.

Safe travels!