I'm moving into a new apartment and will need internet, but NBN isn't available in the area yet so it'll have to be ADSL.
Most of the plans I'm looking at seem to require an active phone line, but I don't really need a home phone/don't have an active phone number, so what should I do?
Thats correct, most require a active phone line.
There are products like iinet naked, which don't require an active phone like. So search for naked adsl plans and away you go.