What is the proper way I should use sublimation until I get stoneskin?
I don't know what the proper way actually is, but I essentially did the same thing as Dominious: Starting Sublimation after standing up and then getting back stored MP towards the end of a fight in order to /heal.
With Clear Mind II, your base hMP is 18, I think. Depending on your gear, your actual hMP might be slightly above 20. You'd get 40+ MP in 30s worth of /heal in this scenario, whereas Sublimation would get 10 ticks (= 20 MP). So better have the Sublimation cooldown timer tick when you're /heal-ing. :-)
1. HQ Elemental staves are a big part of any mages arsenal, which ones are most useful for Scholar?
Auster's Staff > Aquilo's Staff > Pluto's Staff > Other HQ staves.
Pluto's Staff is so damn far behind, because I consider Gravity and Bind much more relevant than Sleep on SCH. Pluto's Staff is nice to have for Drain/Aspir in this scenario, but I rarely had to rely on those spells, because to me the limiting factor was the pet repop timer and BST movement.
Auster's Staff > Aquilo's Staff, because I'm of the opinion that Gravity is the best enfeebling spell in the game and so damn crucial for SCH soro (unless going /NIN for Utsusemi, which I haven't ever done). Exp pt, main healing
: Aquilo's Staff > Terra's Staff > Pluto's Staff >= Other HQ staves.
Aquilo's Staff for Paralyze, Terra's Staff for Slow. Since most mobs you fight after 51 have MP, Pluto's Staff is arguably better than the other ones because of Aspir. I might be wrong with this order, though... "Endgame"
: Pluto's Staff > Aquilo's Staff > Jupiter's Staff > Apollo's Staff > Other HQ staves.
I might be lying blatantly (in all honesty, I had to think for quite a long time to come up with that order), because it depends on what your "endgame" activities consist of. If you solo or low-man many things, Auster's Staff might be still the most relevant one, but since you're "just" B+ in all magic skills, there probably will be some RDM around to toss enfeebles. So you either end up giving around buffs (which don't benefit from HQ staves) or nuking, where those staves get to prove their value. Aquilo's Staff is higher than Jupiter's Staff mostly because of Elemental Magic +10, because of your Elemental Magic B+. Apollo's Staff is listed seperately to give credit to Luminohelix, something I will mention in the next paragraph.
In the end, you will want a full set of HQ staves, because SE gave us equally strong potent nukes on all elements, even Light- and Dark-based: Our helices. While useless on quite a few mobs (those with incredible INT), if they stick for a decent number, they tend to be extremely efficient and generating little enmity.
2. SCHs get there endgame gear from places other then sky and kings, should I be looking into saving points for certain pieces of assault/campaign gear? (What is good endgame gear anyway?)
Good "endgame" gear would be some that makes your nukes feasible (e. g. by letting you hit the 320/120 tier for peskier HNMs), improve the rate you can get to stick enfeebles at (e. g. stuff that raises your Enfeebling Magic skill) or give you more power while party buffing and healing.
As such, pieces of the Yigit set (esp. Yigit Crackows and Yigit Gages) as well as the Goliard set (i. e. Goliard Clogs) are nice to have. Until you get your Yigit Crackows, the Cobra Crackows is a decent piece, too.
For the time being, the rest of your gear sets probably will be some pieces of the Errant/Mahatma set (esp. the Houppelande and the Slops), your AF (you will almost full-time your AF hat, while your Scholar's Gown, Scholar's Pants and Scholar's Loafers are very decent pieces.) and your AF2 (esp. the pieces Dominious mentioned). And a lot of L65 Torques (Dark Torque, Enfeebling Torque and Elemental Torque come to mind).
Einherjar (read: Kilusha in Nashmau) has quite a few useful items for a SCH, too. At 15k, a decent Einherjar LS that runs twice a week can get you an item in less than 2 months.
Other than that, SE is quite pesky; there's not much else a SCH can wear, so it's mostly a best-of put together from Yigit, Goliard, Errant/Mahatma, AF and AF2 sets.
3. As far as subs go it's WHM, BLM, and RDM, but in what situation should I use each of them?
This is my view on SCH75. At lower levels, I might stick with other choices, essentially for Stoneskin on SCH56/WHM28. /BLM:
Unless you do not need any
defensive measures, you could go SCH/BLM for INT+2, MAB+4 and Sleepga in exchange for Stoneskin, Gravity, Blink and Phalanx (there are more differences, but these are the essentials). You also lose quite a lot of your versatility, because there is not much you can do on Light Arts except for curing. No broken things like Stoneskinga, Phalanxga or Enspell-ga. Only recommended if your LS asks you to come for nuking solely, in my opinion. /RDM:
This is where SCH really shines. Both incredible spells to abuse with Accession/Manifestation (aforementioned Stoneskinga, Phalanxga and Enspellga as well as Gravityga and Bindga for massive crowd control) and MAB job trait makes SCH/RDM extremely flexible. You perform well on both Light Arts (healing and handing around unfair AoE buffs) and Dark Arts (nuking and extreme crowd control capabilities). Oh, and you have that juicy thing called "Fast Cast"... /WHM:
I only come /WHM if I feel like Bar-spells might come in handy or there is some real chance I have to be casting Sleep II and
-na at will. You lose on both sides, because your Dark Arts is crippled by puny nukes (in comparison) and a lack of spells like Bind or Gravity and your Light Arts now is reduced to Stoneskin. Being capable of casting Erase or Reraise on Dark Arts as well as Curaga without the use of Accession might turn out to be handy, but scenarios you really want SCH/WHM are rare. I can't see many.