The link that you go with will depend on what you are starting with and what you are keeping.

If you have a single existing account, which already has several toons of 60th or higher level on it, then a chain will be the best method to link with, because you get the most total levels across the team.

If you have five brand new accounts, with no booster on any of them, the chain will still get you the most total levels granted across the account.

If you have minimal characters on the first account, but one of them will effectively boost, and you want to end up with a lot of teams, then a chain is not the best way to go, since the first account will basically end up with half as many toons as the other accounts in the chain.

If you are already a four boxer, and want to go to five accounts, and let's say you already have eight toons on the four accounts... which means you want as many toons as possible on the new account. You might set up like this: A -- B, A -- C, A -- D, and A -- E. "A" being the account which you are keeping to join the existing four, and B-E being disposable new accounts. Transfer a toon to be the "booster" on any of the accounts other then A. Then use this account to boost A + the other three. If you boosted three toons to 60th (lets say A, B, C and D, with E as the booster), then A has three toons already, and will receive 90 granted levels from three different accounts, each of which can boost up to 60th.

If you have two existing accounts, you'd want both to refer, since that way they can each get RAF experience.

If you have three existing accounts, then you'd want to refer from two of the three, so you have four toons with RAF experience, and a booster on the fifth.

In the end, it really depends on how many accounts you are starting with, how many accounts you are keeping, and what level toons you already have on the account(s) you already have.