Don't forget that even characters that are "gifted" levels can still gift to the next account up.

So if you have three in a row:

A linked to B -> B linked to C

C gifts to B and then B can gift 1 for every two to A

Just as an example:
Level 60 on C gifts 29 levels to B raising him from 1 to 30. Now that lvl 30 on B can gift 14 levels to a lower level character on account A. (just an example, not a suggestion)

I've done this multiple times, saves leveling a slow class altogether. The longer the chain the more of a stacking cascade of free levels you will get.

EDIT: Adjusted the gifted levels to the correct numbers.