>>131494Texasfag and adventurer here. Texas is pretty dismal for true "roughing it" and doing extended trips. I usually travel to Colorado or Utah to get my kicks.
However, if you're stuck doing Texas, check out Enchanted Rock or Pedernales State Parks. They're both enjoyable places that offer primitive camping permits at $~10 a night. Enchanted Rock has more designated primitive area.
Colorado Bend SP also has primitive camping available that is usually less crowded than E-Rock or Pedernales. However it is about 2.5 hours NW of Austin.
The best high adventure option in Texas though is the Big Bend region, out in the Chihuahua desert. But that's also like 10 hours away and isn't very practical for a group of friends.