If you intend to build your DpS first, get Virulence. If you plan to tank, get Insolence.
If you aren't sure, get Virulence.
As to what content you should be doing, it depends. If you want to DpS, you can go straight into random heroics (preferably after putting together a crappy DpS set from quest rewards). And, if you ask the tanks if you can roll on the drops, most of them will outgear the instance and let you.
If you want to tank, it's hard to say. I wouldn't advise going into them until you have 25K health, and you need to be comfortable holding threat. You could probably do Reg ToC fine, but it'll be harder than the other 80 regulars (HoL, HoS). It's only slightly easier than heroics though. I advise trying to ramp up your health before doing it.
Leveling your JC up would be great--grab a
Monarch Crab and the
Ruby Hare. Put +30 Stam gems in the Hare, and a +30 Stam and +15 Stam/[Hit or Defense] gem in the other.
This will give you 239 more stamina, as well as a Defensive CD.
You can replace them with
Essence of Gossamer or the
Black Heart (which will last you for a loooong while, unless you are really lucky with raid drops). Naturally, you should replace the Hare first. I'd also probably keep the Crab over the Essence.
Plus, JC will give you an extra 63 Stam from using Dragon Eye's Gems. And getting mining to cap will give
you 50.
So, just capping your professions will give you a total of 352 Stamina. That's a ton, especially considering you won't even have to enter an instance.
Do you have other toons at cap? What factions have they gotten exalted for? Shoulder and head enchants are BoA now, so you can send them to your DK if they're on the same server. Otherwise, you want to get Sons of Hodir and Argent Crusade rep up ASAP. These are worth 37 Stam, 35 Defense rating and 20 Dodge rating.
Also look into the Tempered Titansteel gear.