Gray Butte is very near Smith Rock State Park and is one of the more scenic rides in the area both for the views of Smith Rock and the Cascades in the distance. The riding is relatively strenuous for the most part. It is not too technical except for some loose rocks on the southwest side of the butte on one of the bigger descents. A fair amount of the ride is on dirt roads, on the east side of the Butte and up the Burma Road if you come up from Smith Rock. This area is different than most of the riding in Central Oregon in that it is more desert like with few trees and the trail can get muddy if wet. They also graze cows here so the trails can suffer if they are wet and trampled.
A possible beginner ride would be to start at Skull Hollow and instead of riding the loop counter-clockwise go left on road #5720 (the first real road you can make a left on). Pick up the trail on the right side of the road and go up and over to Sherwood Canyon then turn around and come back. This ride would not be too strenuous or technical but would be fun and scenic. You could also ride up the road to make the climb easier but finding the trail to come back down might be a little more difficult. There is a short section on the ride down to Smith Rock where the single track becomes double track and climbs steeply. After this short climb on a road the single track trail resumes its gradual decent the top of Burma Road. (The Burma road is the maintenance road for the north unit irrigation canal and is very securely gated and locked so do not wast your time trying to see if you can get to it with a vehicle).
Smith Rock is a world-famous rock climbing destination and is stunningly scenic. There are great day hikes around the park. The campground there has good views of the rock but it could be full with climbers. The Skull Hollow campground is not very scenic and pretty spartan but free. You could probably get really drunk and shoot things if you wanted. Expect to share that one with horseback riders, ATVers and climbers on a budget. There are no stores real close so you may want to stock up before you drive out to camp. There are good restaurants and a grocery store in Terrebonne which is 10 miles away. The nearest showers might be the public pool in Redmond. The Crooked River does not look appealing to swim in. It is brown and smells like fertilizer most of the year. It is excellent whitewater kayaking the few times a year when it comes up, however. You would never know this from most of the slack water around the park.