While not as powerful as it once was, Blood is still a solid single-target choice for leveling up, and will provide some extra self-healing that should keep you from spending too much money on bandages and food. A Good solid Blood DPS build will probably look something like this 51/13/7 build.
With this build, you'll actually stick the closest to the traditional, non-talented Death Knight rotation of Icy Touch, Plague Strike, Blood Strike, Blood Strike, Obliterate/Death Strike, although of course replacing Blood Strikes with the more damaging Heart Strikes. You'll want to focus on the Blood tree in this build first, then the Frost, Then the Plague Strike. It may be worth holding back on Dancing Rune Weapon until you can get those non-consuming Obliterates, since that will make your life a lot easier.
One other way to approach this build is to ignore frost altogether, which probably isn't such a bad idea since most of the first 2 talent tiers in Frost are only really amazing for a Frost Build, and dump the points into Unholy, in a build something like this 50/0/21 build. This build doesn't really reach its potential until you can unleash a Hysteria/Gargoyle combination for the burst damage, so it's a little more difficult to level up with, but its worth some consideration. The other thing to remember with both of these blood builds is to watch your Sudden Doom procs. When they come up, use them!
For these builds, you'll probably be throwing out your share of obliterates, so if you're using a good solid hard hitting 2-handed weapon, you may want to consider the Obliterate Glyph. You'll only have 2 diseases up, so chances are that extra 20% off the weapon will overtake the bonus disease damage.