Best advice would be...

During RAF, get a ton of combos to 60th.

Then pick a combo you think will be most fun, and that is your primary.
Possibly bounce between teams, to maximize reseted, but probably just focus on the one team.

Once they hit 80th (or 85th), grind some heroics.
Gear up the toons, so heroics are easier.
Then get the heirlooms for +experience.
And if you want other teams, level those.