You want to make sure every toon is grouped with a toon in their level range who is also RAF linked.
If the booster is your only RAF link, then you're not going to get the 3x experience.

Basically, you need to be within 4 levels (if you're 15th, then 11-19 works) of the other toon.
And neither of you can be 60th.

Your booster can be in the chain with you.
If A is the booster, then B is fine because of the link to C.
A -- B -- C -- D -- E

If A is the booster, then no one gets RAF here:
A -- B
A -- C
A -- D
A -- E