Hey Nmag
There are no trails at Maroochydore as such, but you can go up to Mapleton and there is a tonne of trails (30 mins drive from M'dore). You should take someone local with you here as the forest is BIG - and it's easy to get lost. You can ride an entire day here without crossing the same trail.
Also up at Noosa in the Tewantin State Forest (Woori) there are plenty of trails (30 mins drive from M'dore). Hard to get lost here, so riding solo more applicable.
I can't comment on the Gladstone trails as I haven't been there.
Get on the MTBdirt website and you can see the trail maps & directions there.
Regards
Eyes