Welcome to the best W&W forum anywhere!
I see you have lots of advice here but I am going to throw my preferences for a starter party in anyway LOL! I started with 3 Warriors, A Priest, A Rogue and A Wizard...waited until mid levels (i.e 7-9) to ascend the Warriors to Paladin or Samauri and waited until I had high level spells to change the Wizard to Warlock. The Priest stayed a Priest until the endgame Zenmaster ascension and the Rogue ascended to Ninja as soon as we were headed to Shurugeon Castle and later when he had level 7 spells, he became an assassin.
Hope you enjoy the game as much as all of us have!
Moni