figther -> paladin
figther -> barbar
figther -> samurai
Priest -> monk
wizard -> warlock
and so on...

Here is what I've seen so far..and I wish I did early on..

Warrior - barbarian
Priest - barbarian
Priest - barbarian
Wizard - barbarian
Wizard - barbarian
Rogue - barbarian

I'd do this as soon as you have the stats in each..which should be easy..if you did things the right way..
The reason I would do the above..is simple...EASY requirements for barbarian...
I'd probably go to level 8 in your basic class..by then..you should be able to get into barbarian easy enough...
Then goto barbarian till levle 8..
Then switch to another role...
Ensure you wait on ninja for your last elite for some..and samuari for others..etc...
Remember..once you switch a role..you can't go back to that role..but you can still train in there skills..

Join all guild as soon as you can...should be easy..if you do things right...for each character...2

Remember...it's easier to level the low levels..then it is the higher levels..

For example..I need 57K exp to level at the moment..at my current level...Well..I thinks to myself..
Delmax..change roles..you can get 10 levels of a new role for the cost of one level of an old role...