If you are just starting out. Start with your 3 mages and see how you like it and how your system preforms.

What I presonally did was:

(3) Shamans

(1) Master Account (2) RAF Accounts leveled to 60.

Then using the RAF system created a free 60 Pali.

I was experienced enough to handle another class and now play the Pali (tank) as my main and (3) shamans as my DPS slaves.

Also if you do 3 mages you will have no healing and this is why many people start with shamans just because they dps and heal and ez mode for boxing. When you start to mix in other classes you are making managing all of them more complex.

I have a forumation button but I ONLY use it when I'm doing 5-mans and taking on a pull i need to watch everyone, otherwise they just stay in their normal tight /follow line.