I am looking to add new receptacles (15A) behind my TV by running a 12/2 romex (20A circuit/breaker) from a nearby existing receptacles (15A). The problem is, the existing receptacle has no ground wire. House is old (1960s), I see the that the receptacle is grounded to the metal box (tested this by running a voltage meter touching the hot prong and the metal box).
After doing some research, I came across the possible solution of just getting 15A GCFI receptacles (over buying 2 prong receptacles) for the new outlet and only connecting the hot and neutral wires. This seems to be the "relatively safest" method without rewiring from the breaker.
Is this the best and easy option? Or are better ones out there (again, without having to rewire from the breaker)?