I agree that 100 is a good start. Try to get a ratio of 4 females to 1 male. I started with about 100 adults and 150-250 nymphs 2 monthes ago. I didn't starrt feeding them off until last week and I'm not feeding heavily as I still use crickets and hornworms until the colony is REALLY established.
If you start with 100 don't plan on feeding them off for at least 3-4 monthes.
Good luck,
Kevin