yeah, he's mah boy. most of house hailenarte seems to be pretty down to earth in a good way. i could almost waifu laniatte if she weren't a blade ear or i would and wouldn't tell anyone about it.
the first three open up at 15/16/17 iirc, and then after that you get one dungeon every 4 levels (20, 24, 28, 32) and then one dungeon every 3 levels (35, 38, 41, 44, 47) and a horde of dungeons at 50+. i think there's about as many dungeons at 50 as there are sub-50 dungeons.
like this user said, gladiator is kinda boring early on. and it stays kinda boring until like, level 54ish? or so. sad but true. it's a solid tank class, but none to engaging. to be fair, no class is really engaging pre-20. 20 is when most classes have enough skills and traits to make them interesting; i.e. PGL plays much more fluidly, and by extension is more fun, once you get past level 20 and can stack more than one stack of greased lightning. by end game, MNK (the job that has it's roots in PGL) is a fast-paced, high-skill floor-and-ceiling class that rewards a quick mind and quicker fingers with what is arguably the highest dps in game.
Paladin, the job that comes from GLD, is a solid tank, considered by many to be the "baseline" tank and arguably the most "defensive" of all the tanks, with a plethora of CD's they can pop to reduce damage and protect allies. later game they get a lot more combo potential (3 distinct 3-hit combos) and some solid support, with their own unique super-powerful (1200 potency) healing spell, and a 2 minute cooldown buff that places a shield equivalent to 10% of the pld's life on every ally in a radius. the issue is, it takes a bit to get to that point. even though the prevailing advice is to keep with one class at least until 30, if you're feeling like you need a change of pace, switch it up. play marauder for a bit, or pugilist, or try out conjurer or thaumaturge.
if your wife likes healing, she should start off as a conjurer. that'll place her in gridania, and for the first 15-16 levels she'll be solo more or less, and then the game opens up and you guys can pair up and go conquer the world together. if you're set on tanking, you can't go wrong with leveling marauder, as there are a few skills you get from MRD that make life as a GLD/PLD easier. likewise, if you're set on doing the paladin route, leveling conjurer (the earliest healing class there is) is a good idea, as PLD requires you to have at least level 15 in conjurer, and there are a couple of CNJ skills that serve PLD very well, specifically Stoneskin, which grants a shield that absorbs 10% of the target's life. it's another solid support skills you can use as a PLD to aid your group, that helps set the good PLD's apart from the average shitters out there. there are numerous mechanics in the game that force a healer or DPS to take damage regardless of what they do, and many of these also force the mob you are tanking to stop attacking you. this is where SS shines, as it gives you a way to use your MP that also serves to mitigate damage done to a target while sparing healer MP.
as for the Hall of the Novices, I think it auto-unlocks and gives you a little in-game tip about it once you hit 15. go through all the parts of it if you can, for tank, heals and dps. it's got solid advice, you get some good gear for your class at the level, and most importantly, an amazing ring that boosts your xp gain on sub-30 classes.
yeah, that's about right.