I've copied your post, Sean, and inserted my replies in italics...

Hi
guys, I've been brought to these forums as I've been trying to
propagate some cuttings of various trees around where I live. As
mentioned in the title, I'm quite the novice so any advice/thoughts
would be greatly appreciated. The set up I have is a 24 way divided
greenhouse container purchased from my local hardware store (see
pics). I'm trying to grow several jacaranda cuttings and a few other
trees that look like some fig species (could be entirely wrong here).
Until now, I've just followed some basic cutting instructions from
online, but after a hit rate of 0% after my first batch I assumed I
was doing something. I'm living in Sydney where it is currently
Spring. Some questions:

-
Moisture levels: I have been planting the cuttings in a mix of
vermiculite and purlite (soil-less mixes were suggested) which I give
a spray over before and after planting the cuttings.

Vermiculite
is not a great choice as it contains less air than perlite. Perlite,
being of sperical shapes, holds air (oxygen) which is required by
roots. Vermiculite is isort of in the shapes of rectangular prisms.
Check it out on Google. And therefore it pacts down.

The
first attempt was left in some direct sunlight…

Yes,
this would have cooked the cuttings. Even if the lid had been left
off, direct sunlight is not a good idea.

… which
I believe basically steamed the whole lot. Second time around, I have
kept out of direct sunlight but still exposed to bright light. Should
I be leaving the ventilation slots open? closed? half and half?

Fully
open.

Actual
Cuttings: I have been removing all but around 2 or 3 leaves from the
cuttings I take, whilst cutting the remaining leaves in half or
thereabouts. A few cuttings appear to lose their leaf stems after a
couple of days to a week. Is this the correct procedure?

I
am not sure what you mean by 'losing their leaf stems'. Cuttings
should look like they did when you first made them. Some leaves might
fall off but cuttings should never look wilted, blackened or
frightened.

Mold/barking:
I've attached photos of some white fluff that appears on a few of the
cuttings. I've read this could be a process called 'barking' whilst
others assume it to be mold. Should I expect this and if not, how
should i remove?

I've
never heard of barking. I wouldn't like white fluff about anywhere on
the cuttings. I suspect it is mould. This is a sign of too much
humidiy. In fact, I think even with the vents fully open there might
be too much himidity. I was thinking of suggesting that you prop the
lip up a little to provide even more ventilation.

Blackened
Tips: The ends of some cuttings appear to darken in colour, almost
blackening after a few days as well. I'm assuming the tips are dying
off here but I'm not entirely sure. Does this mean I'm leaving too
many leaves on the cutting?

It
doesn't mean that you are leaving too many leaves on the cuttings. We
always left at least half on. Blackened tips means that the cutting
is almost certainly failing and is best removed. You can fit many
more cuttings in your pots than just one single one.

I'm kinda new to the forum also. But if you will search "easy propagation chamber" on this forum you will get a lot of good information. Read the whole thread.