Job Armour set

[Soulfien]

Do I have to wait until I turn level 50 to get one of the cool armour sets or can I get one upon reaching level 30 and selecting my job?

I'm 2.5 levels away from obtaining Black Mage and all I see is just a continuation of the same cowls and coats I've been wearing since level 1.
I'm currently:
20 Arcanist
27 Thaumaturge
15 Archer
9 Weaver

After this much work, I'm bummed to still look like I did when I started my adventuring career.

[Kanti]

Pretty much. Unique sets start showing up at 45 with the job specific gear you get through job quests, with everything else acquired in level 50 dungeons and raids. The only other low level unique set I can think of is Battlemage around 30 that you get from Brayflox's Longstop.

Stay strong, robeman.

[Anova]

There are unique item sets obtained from the lv.15, lv.32, and lv.44 dungeons. Otherwise, your gear will generally be based off the starting basic sets. You'll notice that the generic equipment tend to have another add-on like a leather strap, or cloth design compared to the lower level version of the same item.

You will also gain job gear from job quests at lv.45 and lv.50.

At lv.50, you will gain the ability to glamour, which lets you change and customize the appearance of any item to any other. Also, the endgame raids and dungeons do give a lot of very nice equipment you can mix and match.

Unfortunately, none of the fashion stuff really starts until 50, when you can glamour. There are no real fashion options until then; unless you're willing to wear lv.1 gear while leveling.

[Niwashi]

You will also gain job gear from job quests at lv.45 and lv.50.

And of these, it's the hat, pants, gloves, and boots that you get at level 45. Then at level 50 you get the chest piece of the set. Given how fundamental the chest piece generally is to the look of a set, you basically get the appearance of the Artifact gear at 50.

In the case of Black Mage, though, the level 32 Battlemage set you can get from Brayflox's Longstop (if you're lucky enough with loot drops to get it) looks good. (Just Google "ffxiv battlemage" and you'll find plenty of images.) It's for all casters, though, and I think it looks a bit out of place on White Mages. (White Mage is the next one I'm leveling, and I'm currently using that one for my WHM set.)

Unfortunately, none of the fashion stuff really starts until 50, when you can glamour. There are no real fashion options until then; unless you're willing to wear lv.1 gear while leveling.

You don't necessarily have to go all the way back to 1. Until reaching 50 and unlocking glamour I generally kept a couple sets for each class: one that had the best gear (stat-wise) that I had available, and another that had something reasonably close but nicer looking. Leveling sets (especially the DoW damage dealer sets, but all of them to some extent) tended to sort of alternate between pieces I liked well enough and ones I found ugly, so if my top gear was something ugly, I'd wear the previous gear from maybe 5 or 6 levels earlier as my "cosmetic" set. Usually, the nicer looking version would only have maybe a couple pieces that were below my best, and if they weren't too far behind, it would be good enough for simple content (like most of the questing). I'd only switch to my top stat set during dungeon runs.