You can get account creation tokens by burning HIVE or spending RC. You always need one token to create an account.
RC numbers aren't really in a format that's friendly for human use. How much a user needs depends on what they plan to do. I think it's easier to think how much HP they need and delegate the respective amount of your RC. So if you have 1000 HP and would delegate 10 HP usually, use 1% of your available RC. I'm not sure how to solve this nicely in the hiveinvite interface yet, for now it only supports HP delegations.
Okay, so I have many account creation tokens, so I can those.
I agree about RC numbers, but thank you for your suggestion, that's a great idea.