2 Tier Affiliate Program design

I am working on a new project and setting up a 2 tier referral program for a membership site and trying to figure out how to weight the compensation for each level when a new member joins. Compensation will be in x number of credits. The credits are valuable to the members but have no real cost to me. My goal is to increase the number of members. Which option makes the most marketing sense?

Option A - placing more value on joining?
Example: 15 credits for the new member
10 referral credits for the Tier 1 affiliate
5 referral credits for the Tier 2 affiliate

Option B - placing more value on direct referrals?
Example: 10 credits for the new member
15 referral credits for the Tier 1 affiliate
5 referral credits for the Tier 2 affiliate

Option C - placing more value on Tier 2 referrals?
Example: 5 credits for the new member
10 referral credits for the Tier 1 affiliate
15 referral credits for the Tier 2 affiliate

Option D - something else?

I would appreciate your feedback. Thanks, Jimmy