I live in manly. going North:
Stop 1 – Ourimbah Forest Park. Its marked (not like UK trails) but good enough. Its a good blast about 12km loop – do it 2/3 times for good ride.
Stop 2 – Awaba. flowy singletrack but short loop 10ishkm.
Stop 3 – Glenrock, Newcastle – you’ll need to hook up w a bike shop and get them to show you the trails, theres a heap of them and they are good fun
check out the NobMob website – it has trail info / directions etc and you may be able to hook up a ride through them as well.
Dont worry about going in to a shop and asking them to show you around trails sort you out a demo bike or something, the scene is very relaxed and people really accommodating.
Happy trails