jumping-off point 
(also jumping-off place)
noun
The point from which a new undertaking or activity is begun: many stations became jumping-off points for hunting expeditions...
- On the drive to Baptism Creek he told us that the point where trips begin are known as jumping-off places.
- Later this year, teachers will begin using that same presentation as a jumping-off point for classroom discussions.
- Although she doesn't see herself working in politics long-term, her current position has been a great jumping-off point.