Confused about classes

[Tarta]

I would suggest with 1 class to Max level, then all your other classes will be easier to level (you will still need Arcanist 15 to unlock White Mage).
However, I also suggest playing what makes you feel best, so if you wanna level dip into all the classes, that's fine too As long as you have fun!

[Keydah]

So what do you guys suggest, should I focus only on my Conjurer for now, or should I lvl THM and later Arcanist?

It's really whatever you feel like doing. You need Arcanist to 15 in order to get White Mage when you hit 30, and you should get Thaumaturge to 26 for Swiftcast (instant cast raising is pretty crucial to healing) but you can get away with waiting to level THM until you hit max level. You should be able to level your healer pretty fast, since you should get queued into stuff within a few minutes. The THM will take longer, because dps queues can be anywhere from 10-40 minutes long.

[Naria]

One thing to note is at least on the Aether data center, DPS queues are shorter than normal atm since so many people are leveling DRK and AST. As I said before, I would recommend at the very least to get Arcanist to 15 before you try to take CNJ too much past 30 as people in your parties/duty finder will may not react well if you don't have WHM unlocked by the time you get to the lvl32 dungeon. Also some abilities for the classes (and all for the jobs) are tied to guild/trainer quests, so it is a good idea to keep those current.

[Vandril]

So what do you guys suggest, should I focus only on my Conjurer for now, or should I lvl THM and later Arcanist?

If you have the patience, I'd consider leveling THM a bit now. It's nice having some cross-class skills early on. It just feels good.

But if you don't want to rush through the level 1-15 range multiple times quite yet, that's understandable.

[Urthdigger]

Honestly, it might be a good idea to try and level up all 3 of them. Up until level 50 when the gear splits off into Healer and Caster gear, all disciplines of magic use the same armor (You'll likely want different accessories. There are some with both int and mnd, but I prefer the more focused ones for more extra stats).