what does "best" mean to you?
You can go up to Skyline, and down Logie Trail or Rocky Point, turn left and get to Scappoose.
You can ride to Vernonia (oooh! Banks-Vernonia Trail!), head out of town on Hwy 47, turn right onto the Vernonia-Scappoose Highway, climb for awhile (summit is somewhere between miles 9 and 10) and enjoy a nice long descent down into Scappoose.
Mapping is left as an exercise to you.