I only have BG1, but the best bang for the buck IMO is a gnome illusionist/thief. The primary reason for this is the specialization bonus spell per spell level. I also maxed out pick locks, so I was able to get the 1000gp gem right from the start (a few import/exports basically means ALOT of early money). Also, in BG1, illusionists are bared only from using necro magic, so fireballs/lightning bolts where memmable.
The funny thing is, by about have way thru the game, I seldom used offensive magic at all, and just hacked things to death or used my main char to sneak backstab most of the mobs. I prefer to go heavier on the healing, which is why I used 2 clerics (that and animate dead).
I enlisted the following NPCs: Ajantis, Coran, Yeslick, Branwen, Garrick. I found that Minsc isn't really worth the upkeep, and I loved the abilities of the paladin better. Coran is just plain nuts, and should be a staple member in any group. At 7th level, I was able to get him to a THAC0 of about 5 using the bow of marksmanship. The sad thing about the bard though, was that he rarely was useful beyond being able to ID all but cursed items. I really like bards, but BG1 didn't really make them all that useful. Let's hope they got a bit better in BG2

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