Here's my suggestion:
Allow everyone to have a quick and easy start. No one wants to be at rotworms for an hour+.
It seems that you're aiming for a long term project, so here are my suggested rates.
Sample rates:
1-8 (50x)
8-30 (40x)
30-50 (30x)
50-60 (20x)
60-70 (12x)
70-80 (7x)
80-90 (3x)
90-100 (2.5x)
100+ (2x)
This will make the first levels (1-50) a lot more tolerable to obtain and not feel like such a grind but again, this is only a suggestion.