Most people go with 14 lost souls = 105 cards. That breaks down to:
40 good
- 4 dominants (SoG, NJ, AotL, GoYS)
- 2 copies of a fort (if needed, like Z's Temple or Garden Tomb)
- 15-16 characters (no more than 3 copies of a unique character)
- 16-20 enhancements (3-5 copies of each card recommended)
40 evil
- 4 evil dominants (CM, Burial, DoN, FA)
- 2 copies of each fort (I usually see protection fort + Kingdoms of the World - Priests, or Raider's Camp, etc.)
- 15-16 characters (including 3+ stand alones, no more than 3 copies of a unique character excluding suicides)
- 16-20 enhancements (3-5 copies of each card recommended)
25 neutral cards
- 14 lost souls (2 of each, especially for the ones with great abilities)
- 5 sites (whatever you like, make sure at least 2 are access sites)
- 6 artifacts (2-3 of each art, as they show slow and leave fast)
That seems to be a pretty good starting point. Just remember to keep good and evil balanced.