its good to know im not the only nz'er on here (hi from christchurch)
if your going to get a smaller car then get yourself an old school suzuki alto (65mpg easy peasy) or if you want something abit bigger, holden barina's are good cars and plenty cheap or if you like old "cool" cars then get a corrolla or starlet. the 4afe toyota corrolla's are good on gas to you can get a respectable 40mpg out of them, my friend gets 55mpg out of his but he has had an ecu tune, custom this and that.
if you want to keep the suby then put a smaller turbo on it, less spool time means acceleration off them mark and better fuel economy (as long as you keep the boost below about 5psi) get a ecu tune as well. and if you want make a hot air intake, seriously theres alot you can do
oh and dont forget to read the modifications page and hypermiling tips.
one last thing. dont forget to keep track of your "milage) ask the gas guy for the reciept with the litres on it
if you were in chch i'd give you discount on fuel but your not haha (i work at bp)