Mundaring Powerlines is a good place to start. It can be a little rough on a stock Forester, but certainly do able. Even more so with decent rubber. There's loads of chicken tracks to help you out.
Also Willbinga, which is just north of Wannaroo. Lots of good winding sandtracks that make their way to the beach. Google it, there's loads of info online for Wilbinga.
Gnagara Pine Plantation is another good spot. It's kind of fenced off but if you look around you'll find a giant pine plantation which you can get to. Loads of guys go in there to ride bikes. Some nice boggy sand tracks through the trees. Good spot to practice using a hand winch too if you have one. Loads of anchor points (ie trees).
Lancelin is great for sand. Loads of sand dunes, but as SKT said, watch out for the numpty dirtbikers. The beach at Lancelin is accessible easily but be careful if you're new to sand dune driving. I rolled my Forester on its side last year when I was wheeling with my girlfriend. Didn't concentrate going down a dune and suffered for it. Well, I just pushed it back over but still...
If you want to make a trip out of it then head down to Margaret River or Pemberton. Margs has a few tracks around the place, mainly heading to surf breaks. Pemberton has loads of light tracks (great for drifting
) and you can get onto the Yeagerup sand dunes. A word of warning. I stripped an almost brand new clutch trying to get my car across Yeagerup dunes. Sometimes it's easy, but when I got there the wind had blown the sand dunes around meaning you had no chance of getting a run up to get over the big dunes. You have been warned
There is also the Harvey Mud Run. A long muddy power lines type track running through the town of Harvey (near collie). I wouldn't really consider trying this in a Forester...that would include even the very capable Foresters that have been built by users here. That place can be VERY gnarly. It's doable, but I've seen some very capable Land Rovers being consumed by that track :rotfl:
Anyhoo, let me know if you want more advice. I've done my far share of exploring around Perth and done LOADS of trips around WA. Feel free to pick my brain. I don't offroad my Subaru anymore, upgraded to a Land Rover and a Hilux Surf, but I'm still into it all.
Also, what type of things- other than the spare tyre and the wheel brace, should i carry on board to keep me out of a pickle.
Go buy a few D-Shackles and a snatch strap and/or tow rope. If you get stuck, people will be more inclined to pull you out if they don't have to use/damage their own gear. I personally wont pull someone out of a serious bog unless they buy my snatch strap off me. Learnt the hard way from being too generous.
A shovel helps too. Go to supercheap auto and buy a dozen el-cheapo rubber floor mats. Good for sticking under your tyres when you get a little stuck.