Lets start by talking about the combat changes and how they affect you, as a mage, well actually read this. That's a lot simpler than me trying to explain it all.
Okay, so we're going to focus on three core things.
Training.
Costs.
PVP.
Quests.
There are many quests that are worth doing throughout your training . . . So here's a list of quests that give magic experience.
Ones that I can see, from eyeballing it, are probably good to do quite early on are . . .
The Blood Pact.
Rune Mysteries.
Rune Memories.
Witch's Potion.
Imp Catcher.
The Grand Tree
Rune mechanics.
There's probably more, but those are just things I figure you'll be able to do rather soon. They don't all give too much EXP, but you might as well get that experience now rather than later since you'll probably want to / have to do a lot of those quests anyway.
On the other hand, maybe you don't give a shit about doing those quests (like me), these aren't the most crazy important things in the world so whatever.
Gear - Weaponry.
Infinite air runes is a wonderful thing, good for lower levels when you don't have better options.
This is a quick but similarly weak upgrade from this, offering infinite air runes (or water/earth/fire for that matter, but only one rune type at a time).
This is basically a tier 30 staff of air.
This is basically a tier 40 staff of air!
After this point you'll be seeing far less infinite runes.
This is a tier 50 staff maybe, they might have gotten nerfed. It was either the SC weapons, SC armour, or both. Can't remember. Either way, kind of a pain to get and you probably want to skip this one.
If you're itching for a tier 50 magic staff, this is also an option but it requires a lot of time investment as you'll need to beat Desert Treasure which has many pre-requisites.
Unlike the sacred clay staff, though, this may actually be worth your while because you definitely want to do desert treasure some time or another whereas SC is not really going to get you much else than some junky BXP and bad equipment, at least for magic anyway.
These tier 60 staves are obtained at the magic arena, which is pretty dangerous for a lower level, but I think you should be able to pull it off given the generally low population.
As I understand it, the guthix staff specifically is the best but it is up for debate I suppose.
It lowers the defense of your enemy, which is better than lowering their magic in PVE and of course lowering the enemy's pray is also useless in PVE, those being what you get from Zamorak and Saradomin's staves respectively.
As far as PVP is concerned, they're all quite junky but from what I hear the saradomin is particularly junky, because it doesn't reduce prayer points well at all.
Guthix is reasonably useful, as you'd expect lowering the enemy's defense just lets you be a bit more aggressive.
Zamorak is actually pretty useful too as you are reducing their damage and can potentially throw them off by preventing them from using the spell they otherwise would autocast.
All of these have a pretty steep reclaim cost for a lower level, that being 80K, so it'd be best to not try to lose them.
You also need to cast divine storm 100 times in the mage arena before you can even spec with them, but this is easily accomplished without even risking runes as it requires only air runes and so you can just use a mystic air staff to cast it.
An obsidian staff, a buyable and altogether safer option compared to the god staves, it is also tier 60. There's no spec for it but you also don't need to go through the hassle of getting it beyond buying it, which is nice.
A tier 70 staff! Pretty expensive, we're talking 700K minimum probably, but it's quite a big step up from tier 60. and it degrades with rather steep repair costs. Moreover you probably won't even want to keep it that long, so the cost of buying it then selling it may also make things more expensive . . .
All in all, it might be worth skipping this thing, especially if you're still short on cash by the time you get to level 70 magic.
This thing is great! It saves runes, it's tier 75! And . . . It costs like 4M+ and yet has the protect value of like 150K last I checked . . . Ouch.
It also has a pretty nice spec that heavily reduces melee damage but . . . It's got a protect value of 150K. So. Yeah.
It's good, it just is a bit dangerous and/or forces you to use worse gear in other departments in order to not lose it. Especially if you skull.
This is a nice alternative to the staff of light, it's tier 75 as well but actually has a halfway decent protect value.
It can also cast polypore strike, a decent tier spell, on lunars which means you can also cast vengence. Not too useful in teleblockscape but it's there!
They cost around 2M, usually. Might be different now-a-days.
This is quite an oddball - it's a t75 staff that can carry runes (and as I understand, protect these runes in the case that you protect the staff but am unsure about that) but also requires level 90 runecrafting.
Thing about these little guys is they're pretty cheap compared to polypore staves, probably under 1M.
This is a powerful (tier 77), but extremely expensive (~30M), staff with one of the best specials in the game.
Unless it's different on Darkscape it should hit 4 times in a row more quickly than usual and hitting harder than usual. Wikia says
Four attacks are launched in quick succession against the opponent, each hitting for up to roughly 150% spell damage.
Costing only 50% specbar to use, this is almost like the dragon claws of magic . . If dragon claws were still good and apaprently they aren't s I understand it but anyway.
Specifically, but much like a lot of things on the wikia it doesn't necessarily translate well into legacy (which is the combat system that what we use).
Another great thing is that this staff provides infinite air runes, making it a great way to keep rune costs down in the later levels.
This is also a powerful staff with a fantastic spec, but it's quite different from the armadyl battlestaff. First off, it's tier 78, more importantly . . . It's price tag is far lower. But even more important than that! It degrades to dust after an hour of combat.
A magic attack is launched at the opponent, dealing up to 200% weapon damage and reduces their attack speed temporarily.
It costs 100% spec but it has much better burst and can slow their damage down, which is great in Darkscape because slowing down the damage you take helps you win the war of supplies and become the aggressor instead of being more evenly matched against more powerful enemies.
For PVP, this thing is heavily underused (probably because risking much of anything's a waste of time to most people), but if you want to focus a lot on magic it'll be very good.
These both require you to pay insane amounts of money (40M+, 100M+ I'd estimate) to get your hands on, but because weaponry over T75 has received a bit of a tone-back for Darkscape and because they cost a lot to repair over time . . . They're probably not something you should worry about ever getting.
Tl;dr of Gear - Weaponry
Staff of air(1)->mindspike(air)(1? 5? wiki has conflicting numbers)->air battlestaff (30)->mystic air staff(40) to take advantage of the free air runes while not losing out on power compared to alternative staves.
Level 50: Get ancient staff if you want to do DT early on, the sacred clay staff might also work but it might be nerfed.
Level 60: get a god staff or if you don't want to bother (it's fun, come on!) get Toktz-mej-tal.
Level 70: ahrim's staff is a big jump up but costs a lot. Consider skipping it if you're poor.
Level 75: staff of light is expensive and has a low protect value, but is the best for long term use if you are comfortable. Greater runic staff is the cheapest and can store runes (potentially protecting them on death, not sure) but requires 90 RC. Polypore is relatively cheap, good protect value, and no other requirements.
Beyond level 75: stuff that probably doesn't matter.
Almost at the character limit, moving on to another comment.