Alright, so the first trail on the right leads to this small dirt bowl with some smaller jumps (big enough for me) where you can have some fun. In the middle of the bowl, if you take a left, you'll hit some of the fastest single track in the Gyro, which has wider turns, is mostly flat, and with some nice dips here and there. Also a long 2 x 4 that clears a gap you can skip if you're not comfortable with it. Follow the track and it will come out close to the river (this is also where one of the other trails connects, so be on the lookout for other bikers). Take the track along the lake and continue on (you'll see some smaller dirt jumps), ride over the see-saw, and you'll be out of the system and amidst some small houses. You're back out on the road. Take a right, and you can go back to the gas station.
The second trailhead on the right begins the twistier single track where you'll have to watch your handlebars and weasel through some tighter spots. This track is the longest, goes all over the place, comes out close to the river, but then turns back into the woods. The trail will pass through a clearing and end up where that first trail comes out. You can either continue on toward the river and finish out on the road, or you can turn on the faster single track and end your trip with the dirt bowl and come back out on the dirt service road. The trail on the left is not very twisty, it's quite short (fun too), and will pass by an impressive BMX/DJ section, before coming out in the parking lot of the first gas station you had earlier passed. Try to turn it all into a big loop!
Optional: If you want, keep taking that dirt service road back, go over an old bridge with holes in it, and into a field. Best in the springtime when the grass is lower, but still very Little House on the Prairie any time of year. If you see ATV/bike tracks, follow them and watch out for animal dwellings. This leads (hopefully) to gravel road that you climb to a paved road. Take a left, go down the road, take another left onto the next road (175), and ride back into Plymouth.