Many options possible, depending on your style and alignment. I'm going to assume good/neutral alignment, and suggest characters that are available relatively early, so you won't have to change things around in chapter V.
PC
Imoen
Khalid (fighter, Friendly Arm Inn)
Jaheira (fighter/druid, Friendly Arm Inn)
Minsc (ranger, Nashkel)
Dynaheir (mage, Gnoll Stronghold)
Given events in BGII, this seems to be the party you are "meant" to use. A disadvantage is a lack of healing power. An alternative to Khalid and Jaheira is Ajantis (paladin, area north of Friendly Arm) or Kivan (ranger, High Hedge) with Branwen (cleric, Nashkel Carnaval, bring a Stone to Flesh scroll).