So, 2.4 is live, (some of) the servers are up -- did you really expect things to go smoothly? -- and you're raring to head to the Isle of Quel'danas and start kicking some legion behind in the name of justice and awesome badge loot. But before you go, just remember that you can't do it all on the first day. That's not only because you have to take a break from WoW sometime, but because there's a few things that will only be unlocked for your enjoyment with time and/or completed dailies.
Teleport directly to Quel'danas from Shattrath - Unfortunately, You can't count on a portal to Quel'danas straight from the start. You'll want to teleport to either Ironforge or Silvermoon City, and take the Gryphon up to the Isle of Quel'danas. Luckily, the flight isn't horribly long. Once the 2nd wave of the Shattered Sun Offensive begins, you'll also be able to do a daily that starts in the middle of Shattrath and will send you to Blade's Edge Mountains to collect Smuggled Mana Cells. Once the daily has been done enough times by enough people, you'll get a portal straight to the offensive.
Buy badge loot - I'm sure by now you've been able to figure out exactly what badge loot you want to pick up with the help of WoW Insider. You might even have enough badges already saved up for a couple pieces. Unfortunately, you'll have to wait for Smith Hauthaa to show up once the Armory is taken, and then do her daily quest for the ore she needs to set up shop. Once the combined efforts of your server have gotten her enough ore, you'll be able to get yourself that Crossbow of Relentless Strikes. In the meantime, look at it as an opportunity to grab some more badges!
Buy epic gems for badges - So the badge gear isn't your thing, or maybe you'd rather min-max out a couple of your existing pieces before you go upgrading, and you want to buy some epic gems. You're still waiting, sorry. In this case, you're going to have to wait until the Island is nearly completely retaken. Then you'll have to collect Razorthorn root for Mar'nah until she's got enough to get her friend Shaani to start churning out the gems.
Kill Kil'jaedan - Yeah, they removed the Essence of the Immortals, but even if you have 24 more people who've got inside information on all the bosses and are just raring to have a go at it, you'll have to wait. The last we knew, they still plan to gradually unlock the Sunwell at set time intervals. You'll have to whet your appetite on Kalecgos and Brutallus for a while before you can take on the big guy himself -- though hopefully not too long, I'm sure a lot of people want to flush Kil'jaedan down the Sunwell before we head to Northrend.
Don't fret too much, there's plenty to do, be it the first round of Shattered Sun dailies, the Shattrath dailies, or Magister's Terrace itself. You'll find plenty to keep you busy, and if your server's diligent, you won't have to wait long to experience the full potential of patch 2.4. Enjoy it!