Why start with ? Because Season 1 is widely considered the purest version of the show. Later seasons introduced mythology arcs, a sinister "Dark Side" of the spirit world, and major character deaths. But Season 1 is grounded. It is about a newlywed woman in a small town who simply wants to help.
Watching the first four episodes on DVD 1 back-to-back reveals a subtle character arc: Melinda begins as a woman hiding her gift, but by "Mended Hearts," she fully embraces her role as a bridge between worlds. Ghost Whisperer- Season 1 - DVD 1