Jagen,
Before you start posting trademe links to every car you find on trademe, do a bit of google research on what you are looking for.
this is "E90 BMW" "N42 engine" "N52 engine" etc.
Also you need to identify what is the most important to you in terms of options/spec when looking for a car.
Key things to consider are: NZ NEW or import (usually Japan but sometimes Singapore), Motorsport spec/highline spec/standard spec, leather interior or suede fabric, sunroof, iDrive system, LCI (also known as facelift) or not LCI (pre-facelift), petrol or diesel, etc etc.
Glenn is your man if you - find a car you like and after driving it you are happy to purchase it, BUT you are not 100% sure about the mechanical condition of the car so you need to get a full proper professional "Pre-purchase inspection" done on it to give you peace of mind that you are buying a good condition car not one with underlying hidden problems.
Some basic notes for you:
320i = 4 cylinder - Stay away like the plague
325i = 6 cylinder - Good engine but there are some bad examples so try to find one with some service history and preferably from a good owner.
Dont believe the trademe advertisements 100%. Lots of dodgy dealers advertise their cars as "MOTORSPORT SPEC" or similar but are just selling a standard poverty model with dressed up wheels or M badges. If you are unsure, post up a link - we can identify which is the real deal and which is a fake quite easily.
Dont worry too much about Kms, focus more on trying to find a NZ New or one that meets all your other options and get a PPI done with Glenn once you are fairly certain that it is the car for you. (I would rather have a car thats done 130,000 kms in excellent serviced condition than a fresh import from japan thats done 20,000kms and pay a $5000 premium)
Lastly, although we are here to help you make an informed decision on what to buy, at the end of the day, you cant forget that you are buying a BMW - this comes with sudden and unexpected bills and sometimes expensive repairs. You should and need to be prepared to have some spare cash in your pocket for emergencies so dont think you can buy the most expensive, newest, lowest km BMW and expect trouble free motoring for 5 years. Its just not going to happen.
Welcome to the forum lol.