new player, trying to decide on class

[Anova]

If you want a quick way to level, palace of the dead is probably the fastest way. It can be unlocked by completing the quest, the house that death built.

You can also use hunting logs, fates, and guildhests (they reset for every class, so you get the first clear bonus every time you do them on a new class/job). You can also try PvP, although the pvp skill list is undoubtedly more about damage than support

Dungeons also give a lot of exp, especially with the +100% exp bonus that's possible from killing monsters. However, your queue time as a dps will likely be atrocious in solo-queue. If you can run with a tank/healer friend, it's also a good way to level, especially when you're 50 to 70, as that is when you start gaining most of your unique support abilities.