Lancelin, Wedge island. Shitloads up there, spots to camp and what not aswell. Been up there many times, theres a lot of bush tracks and large area of shifting sands with good hills, decents and JUMPS!!!
Also go along Toodyay Road and when you get to the top of the hill there is a gravel turn off. Its easy to miss but theres some nice tracks through there. Kalamunda Powerline track aint bad either.