3x a week
about 30-45 minutes a session
Bench Press 5x5
Bent Over Row 5x5
Overhead Press 5x5
One week do ABA (mon/wed/fri for example), next week do BAB.
To me that is pretty close to bare minimum requirements to grow at an effective and efficient pace.
Another routine example for bare minimums would be Jim Wendlers 5/3/1 (google)...
5/3/1 Bench Press
That is one of the most basic routines that is still an effective strength gainer.