Couple of questions

[mbreen100]

Right now I'm a 16 ARC but I wanted to switch to CON to heal, I know later on ARC can become SCH so should I just stay with ARC for time being? Also I started out in Limsa Lominsa are all the guilds there to switch to would I even be able to switch to CON? I played ffxi and I forget when you open up the "subclasses" but is that level 30 here when you have 2 class and subjob? Thanks in advanced!

[Enkidoh]

Welcome!

Really, it's up to you how you progress through the game, although as you know to gain a Job later you need to have level 15 in a second specific class to do so, so it is helpful to actually get that levelling out the way beforehand (you actually get an increase to exp gained in battle if your first class is higher level than the first, which helps a bit.).

As for your second question, unfortunately each class only has one guild in one particular city (this determines what city you start the game in), so if you want to unlock other classes you will need to travel to the other two cities to do so. This is the list of where each class guild is located:

Limsa Lominsa

ACN (Arcanist), MRD (Marauder), FSH (Fisher), ARM (Armourer), BSM (Blacksmith), CUL (Culinarian)

Ul'dah

GLA (Gladiator), PGL (Pugilist), THM (Thaumaturge), WVR (Weaver), ALC (Alchemist), GSM (Goldsmith), MNR (Miner)

Gridania

CNJ (Conjurer), ARC (Archer), LNC (Lancer), BTN (Botanist), CPR (Carpenter), LVR (Leatherworker)

Hopefully this has helped.

[Erendis]

When you reach the story point when you have to travel to Gridania, You can learn conjurer there. There also will be some side quests that will help You gain a few first levels, and hunting log with Fates should help you reach level 15 easily. That way You could continue doing story quest while being a conjurer (if you really want to switch).

Two jobs are currently only available to arcanists (Scholar - healer and Summoner - DPS). You can learn jobs at level 30 after you leveled required second class.

[mbreen100]

Thank you both so much that did help a lot

[Sagittarian]

You can pick up as many classes/jobs as you want, so don't worry about that part. You just need to register at the guild in the appropriate city (see Enkidoh's response).
To unlock Scholar as an Arcanist you will have to get Conjurer to 15 anyway. If healing is what you want to do, I'd say start Conjurer once you unlock the airships and get to Gridania. That will give you a feel for it and then you can decide if you want to go back to Arcanist to unlock Scholar or stick with Conjurer for White Mage (which requires level 15 Arcanist, so those levels are a 'waste').

[Highlanderx]

That will give you a feel for it and then you can decide if you want to go back to Arcanist to unlock Scholar or stick with Conjurer for White Mage (which requires level 15 Arcanist, so those levels are a 'waste').

Leveling sub-classes are never a Wasteyou gain access to more cross-class skills, Some of which if you don't have while doing end-game content your gimping yourself and the party. And most class require a higher level than 30 to learn all their skills available for cross-class.

[ColorOfSakura]

Cross-class training is necessary to get the upper level jobs (like Scholar and White Mage), plus it helps you net additional abilities for you current class.

Also, if you're playing a healer, you'll want to cross class train as a Thaumaturge as well because they get two abilities that will be invaluable to you later on: "Surecast" (The next spell you cast will not be interrupted *unless* you're moving) and "Swiftcast" (the next spell you cast will be cast instantly).

Also something to be aware of when choosing a Healer class:

White Mages/Conjurers are a bit easier to play, their single heals are more potent and there's less mechanics involved in playing them - however their drawback is that they don't have nearly as good damage mitigation or prevention.

Scholars can actually end up being more powerful healers if they are used at their full potential, but they are quite a bit more complicated to master and there's a lot more mechanics to focus on.

[Enkidoh]

Surecast I find is on such a small duration to actually be of any real use though - as you never know when you'll be interrupted, it effectively a wasted ability slot (not to mention the chance of being interrupted when casting a healing spell is actually very small now due to tweaks SE has made since the Beta, unless you happen to move while casting). Swiftcast on the other hand... it's value simply cannot be understated. Used with Raise (or Resurrection) and bam, instant raise. It's probably the most useful cross-class ability in the game really.

So it's well worth taking THM to level 26 simply for this ability alone (Blizzard II can also be useful when soloing, but it's not really needed when you're in a party as CNJ/WHM).