Is that part of the blue trail legal? Pretty fun lil romp right there.If you are just getting started then I would suggest going up the RED (Cannonball) to the lake and then around the lake and back. See how you feel and if you like it, then you can start exploring more. If you want to add a little more you can try the BLUE from the Lake to the lower parking lot in Skyline and back too. You can stop at the big drop before the lot (You can't miss it)
Have Fun!
Here is my best effort at a map of the Skyline Dr. trails.
If you put it together with the RVCC Ringwood map it covers the whole Ringwood trails.
Sorry, no fancy motionbased/GPS data.