I checked the miles you get with Air New Zealand with TK:

Y,B,M,H,E,Q,T,V,U,O,A %100

W %50

Now, depending on the route you fly you would be *Gold with TK after 3 to 4 one-way trips and get Elite Plus status easily with your 4 round trips.

But of course that's speculation without knowing the carrier and the route you are going to fly.