Not enough information to answer the question. I'd ask the civilian for more information. There needs to be a qualifier:
...to impress chicks/dudes?
...to audition for a [insert genre] band?
...to get a handle on Rhythm changes?
...to work the muscles in their fretting hand left pinky?
But my mother taught me that there are no "shoulds," so here's a stab at "...to have fun on the bass while also having a long opportunity learn." If I could only play 5 or 6 tunes for the next 12 months, these would keep me busy and engaged:
* YYZ or Roundabout (either)
* St. Thomas (chords and head)
* Santa Fe, from RENT! the Musical (but maybe this one because I learned it last year and I still dig the arpeggios)
* Trading My Sorrows
* Stormy Monday
Also something by the Beatles, but I can't put my finger on the best one to pick.
Disclaimer: limited exposure to rap, classical, and heavy rock genres here, so I'm certainly not spanning the available catalogs of all good bass music, ever.