I found it was easier as I began multi-boxing to stick with the same class. Setting up your macros and getting accustomed to multiple characters is hard enough when they all have the same spells. Also, melee are much more difficult to control due to line of sight issues. Having more than 1 melee is a challenge. So along those lines, i'd recommend 3x range casters or 1xhealer and 2xranged caster to begin with.

Of course, there are people who just go straight for 5 boxing using 5 different classes. So don't feel you have to take the easier route. I would still recommend not using more than 1 melee class though.