Gearing up is the biggest challenge any freshly level 80 WoW player faces. Death Knights are in no way exempt. We may seem incredibly overpowered as we level up, but once 80 its a pretty level playing field, and we're expected to pull our weight. Before entering into any end-game raids, even a 10-man, it is important to improve our gear considerably beyond the various questions and dungeon blues we've scraped up while leveling. Most raid groups want you to have, at the very least, level 80 superior-quality gear in every slot. A great way to do this is through purchasing level 80 BoE blues and epics. Most level 80 blues are often under 100g on the AH, and many epics are available for under 400g.
Having a blacksmith craft gear for you is also extremely helpful. For example, the Titansteel Destroyer is a great crafted weapon, on par with many 10-man Naxxramas drops. Other epic and blue items can be crafted by blacksmiths for both tanking and DPS, like the Spiked Titansteel Helm or Tempered Titansteel Treads.
The number one way to get gear pre-raids is through heroics and heroic badges. Try to rid yourself of low level items and greens before even entering heroics, especially if you're going to be tanking. Finding good gear upgrades is often as simple as going to the Armory and using the "Find an Upgrade" feature. The only problem is that this feature often won't differentiate gear for whether you're a tank or DPS, hit or expertise capped, or not. For that reason, it is important that you understand Death Knight stats - so that you can easily recognize an upgrade on site and not rely on someone or something else to tell you which is better.
