The [item]Frozen Shadoweave Shoulders[/item] will be the main target of frost mages that took the path of Shadoweave tailoring. If you're not a tailor, a good placeholder for them are the [item]Spaulders of the Torn-heart[/item], which you can get from a chain quest in Shadowmoon Valley (you'll need a group for it and its preceding quests though). Once you get to Honored with Aldor or Scryer, you can get [item]Inscription of Discipline[/item] or [item]Inscription of the Orb[/item] respectively as a shoulder enchant. At exalted, you'll have the option to enchant your shoulder slot with [item]Greater Inscription of Discipline[/item] and [item]Greater Inscription of the Orb[/item] so try and get the shoulders you aim for before reaching this reputation level:

Tailor mages will go for [item]Frozen Shadoweave Robe[/item] or [item]Spellfire Robe[/item], depending on their spec. However, these items take some time to create since they're quite costly and not every mage is also a tailor. If you have some gold put aside, you can start off with buying the [item]Robe of the Crimson Order[/item] from the AH, or get the [item]Robe of the Great Dark Beyond[/item] from Heroic Mana Tombs. Here are some alternatives:

Fortunately, with a little World of Warcraft gold, you can easily buy some nice cloaks off the AH without too much of a hustle. The [item]Cloak of the Black Void[/item] for example is a tailoring BoE craftable and it doesn't require mats that are way too expensive, so look for someone that can craft it for you (for free, or a fee). [item]Terokk's Wisdom[/item] is another good BoE, but you'll probably have to pay a hefty sum for it. Anyways, here are the alternatives you have:

For a cheap BoE tailoring craftable that you can get at level 69, the [item]Bracers of Havok[/item] are surprisingly good. The nice Intellect boost and the high spell damage for a bracer item make them a great placeholder. The [item]Bands of Rarefied Magic[/item] in Heroic Shattered Halls are a nice goal for any mage, but you do have some alternatives in-between:

The [item]Spellfire Gloves[/item] are an excellent choice for an Arcane/Fire mage that chose Tailoring as one of his or her profession. As a start-up item, the [item]Gloves of the High Magus[/item] have great stats and spell effects, but the quest chain to get them is a bit long. I suggest you invest some time in them though, as they'll keep your hands warm for a while. Last but not least, the [item]Energis Armwraps[/item] from normal Botanica should be one of your main instance-grinding targets. Some other options include:

[item]A'dal's Gift[/item] is a quest reward that can be obtained in under a day from the chains, so you might want to go for it as a start-up. When you get some money on you, try buying the [item]Sash of Sealed Fate[/item] from the AH, which is almost comparable to [item]Girdle of Ruination[/item], a much more expensive BoE (this one is craftable though). Tailor fire/arcane mages will want to go for the [item]Spellfire Belt[/item], naturally. Here are some other waist items you might be interested in:

The [item]Imbued Netherweave Pants[/item] are a great start-up and they're usually quite cheap, since people craft them for leveling tailoring and sell them for peanuts. You will eventually want to get the money for either [item]Spellstrike Pants[/item] or [item]Battlecast Pants[/item]. I'd personally go for Spellstrike, although they have smaller stats and the same amount of spell damage. They have one more gem slot though, spell hit and spell critical ratings and a consistently better set bonus than the Battlecast one. Remember to put [item]Mystic Spellthread[/item] or [item]Runic Spellthread[/item] on your pants if you plan on using them for a while:

As a placeholder for a while, you can use [item]Imbued Netherweave Boots[/item], which are quite cheap to make. Unless you're a frost mage tailor and can make the [item]Frozen Shadoweave Boots[/item], your best choice is grinding Heroic Slave Pens for [item]Boots of Blasphemy[/item] or [item]Boots of Ethereal Manipulation[/item] from Heroic Botanica. Some alternatives:

The [item]Band of Frigid Elements[/item] or [item]Khorium Inferno Band[/item] or [item]Arcane Khorium Band[/item] can be great start-up ring items since they are BoE craftables and the last two work great in combination with the Spellfire set for Fire/Arcane mages. Eventually you'll want to aim for [item]Cobalt Band of Tyrigosa[/item] and either the [item]Seer's Signet[/item] if you're Scryer, or the [item]Ring of Cryptic Dreams[/item] from G'eras Heroic Badges an Sons. A lot of alternatives for placeholders though:

The trinket slot(s) will be problematic, because you have a lot of items too choose from and it will be difficult to set a grinding target. One good start-up trinket to replace those old level 60 ones, [item]Vengeance of the Illidari[/item], can be acquired from a group quest in Hellfire Peninsula. However, your main target, especially as a deep fire mage or a Shatter Frost mage should be [item]Shiffar's Nexus-Horn[/item]. I found it to proc often enough to make it almost irreplaceable and since it has no 'Use' ability, you won't have to worry about forgetting to proc it (and let's face it, we often forget to proc our trinkets in mid-fight) and you won't have to worry about the shared 'Use' cooldown with another trinket. The other trinket could be either [item]Quagmirran's Eye[/item] in Slave Pens Heroic or [item]Icon of the Silver Crescent[/item], obtainable with Heroic badges. [item]Figurine - Living Ruby Serpent[/item] and its high stamina/no passive effects looks more like a warlock trinket, but you can use it as a placeholder if you've got nothing to put in the other slot yet (it's BoP Jewelcrafting though). Here's a list of other useful pre-raid mage trinkets:

It's easier to solve the 1handed + offhand versus 2handed staff debate for mages, than it is for priests and warlocks, mostly because of the G'eras Heroic Badge offhands which are great for specific spell damage gear setups. Since there are no staves with specific spell damage like +fire, +arcane, +frost, getting the G'eras offhand of choice becomes a priority for any mage. Since there are no specific damage school main hands, you'll have to aim for +spell damage and stats. The [item]Blade of Wizardry[/item] is an awesome main hand, but it's best used in conjunction with [item]Quagmirran's Eye[/item] for the superb spell haste increase. If you've got the money (and yes, 2 Primal Nethers + 8 Primal Mights + other mats cost a hell lot) get [item]Eternium Runed Blade[/item] or simply grind Honor Hold/Thrallmar rep like a madman for [item]Blade of the Archmage[/item] or [item]Stormcaller[/item] respectively (they're called differently for Horde and Alliance, but as you can see they're virtually the same item). Here's an extensive list of offhands and main hands to use:

If you choose to use a staff, you can start off by either buying [item]The Bringer of Death[/item] off the Auction House (not that expensive on the servers I play/played on at least) or grind Black Morass for [item]Bloodfire Greatstaff[/item]. I'd personally save my money and go for the [item]Bloodfire Greatstaff[/item], since Black Morass is a relatively quick instance and many people are looking for multi-runs there for reputation (you may also need the reputation for some other items, such as the [item]Continuum Blade[/item]). For the ultimate pre-raiding staff, you'll have to grind Sethekk Halls heavily in Heroic mode for [item]Terokk's Shadowstaff[/item] and hope to get lucky:

If you're Horde mage, try going for [item]Rod of Dire Shadows[/item] as early as possible, it's a quest reward so it shouldn't be that much of a problem to get. For Alliance mages, a good start-up placeholder is [item]Nexus Torch[/item], which has a fairly good drop rate in The Shattered Halls (Normal) so it shouldn't be too tough to get either. The [item]Wand of the Netherwing[/item], has no Intellect, but the DPS, Stamina and Spell Damage on it makes it worthwile grinding normal Shadow Labs. [item]The Black Stalk[/item] is a wand that will keep you comfy for a while even after you start raiding, but it's harder to get since it's a rare drop from Heroic Underbog: