Hmm, let's see... So, what I like about the Ciara is that it moves well, because of the merino (it's not as restricting as a similarly-styled cotton or linen shirt) - I'd have no trouble biking in it, for instance. But, because of the princess seams, it looks sleek and a little dressier than throwing on a straight polo shirt. I wear it over a tank and jeans, but also over a short dress for a slightly more put-together look. In the winter I could totally see adding leggings and a coat to the dress ensemble. As for size, I typically wear a US size 4-6 in tops, so if you're an 8, you might want to size up to a M.
The Trinity looks a lot like the long-sleeved version of the Ciara. I really want to try it but will be a good girl and wait for a sale.
I had the Noe, tried it on, and ultimately sent it back. Loved the Astro Blue color but the neckline didn't work on me.
Do you have your heart set on some Ibex? I usually choose between them based on which colorway I like better... most of their items have equivalents in each other's lineups. (e.g., Shak Lite Hoody = Quantum, more or less) I wonder if Icebreaker will be cheaper in Australia, given that they source their wool from NZ. (I have no idea what shipping is like from NZ to Australia, though.)
More comparisons... I have an Ibex short-sleeved tee, the Sol, which is similar to the Icebreaker Tech T Lite. The Sol seems slightly more see-thru to me, but it's also pink, vs. the teal blue and black of my IB tees. So I just have to be careful what I choose to wear underneath it (light-colored undergarments).
Long story short - if you forced me to come up with a short list of essential merino pieces, I'd say:
1-3 lightweight (<150gsm) tank tops (Icebreaker Sprite, Sprint, or Aero; Ibex Synergy X or Wrap tanks)
1-2 lightweight short-sleeved tees (IB Tech T Lite; Ibex equivalent)
1 midweight (200-260 gsm) long-sleeved half-zip hoody or shirt (no hood; e.g. IB Oasis; Ibex VT Hoody also fits in this category to my mind, though a full-zip) OR a button-down (Ibex Ciara)
1 long-sleeved hoody (Quantum, Cascade, Shak Lite)
1-2 dresses (IB Muse, or Villa; Ibex Circle, Synergy, Lineup)
lightweight merino leggings (3/4 or full-length)
(the above is roughly the same as my capsule wardrobe, which was essentially my packing list for a three-week trip we took this summer. We didn't go to any cold climes, but if we had I'd just add another long-sleeved shirt, a thicker hoody, and a down jacket.
- and, a caveat that I don't know as much about Ibex. I've listed Ibex equivalents above, but I haven't necessarily seen them all in person. There is an Icebreaker store near me, so I have tried on more of their items.)
I'd say the key thing, in order to minimize returns, is to know what silhouettes work on you. (besides knowing what activities you will need them for, which you've already identified.) I don't like crew necks, very deep V necklines, or anything flowy and billowy. Drop shoulders and cap sleeves are also a no-no for me, so I don't even bother trying them on. Other than that, just go with the colors/styles that speak to you!