Your answer will depend on the ballistics of the caliber you are shooting. You might as well get started on the next phase of your learning curve. Go to this page on LRH and choose one of the ballistic software programs:
Ballistics Programs (Web based & Downloadable)
Enter your data, based on your load (or expectations). The software will give you the MOA that need to be dialed in to hit your target at various distances.
If you have 68 total MOA range in you scope, then roughly half of that will be available to you (usually a little bit less). So call it 30 to 32 MOA of travel. That should get you out there quite a ways.