how low do ultra lows and superlows make your car? and what is the legal limit again 150 mm or somthin isnt it?

Legal limit would probably differ in different states as road rules are state made.

Any 1 no the legal limit in vic?? its somthin like aslong as coke can fits under? and yeh what would b good for a AU on 18s?

Very basically it's 100mm, but it's alot more complicated then that, different height depending on distance from axle.
Vicroads website has the measurements.
I reckon ultras with a coil off would be good for an AU with 18s, but thats personal preference LOL
Personal taste dude, look around for pictures of AUs and make a decision.

thanks every 1 for your imput i also agree personal preferance but some peoples preferences just dont work..