Bloods are far and away the best way to learn how to *really* play Stellar Crisis. You have no ally to rely on to bail you out and nobody else to blame for your problems. Because you are often fighting on several fronts, you are forced to quickly learn the fine arts of both attack and defense. As a new player you will be nuked and nuked often, but you will learn very quickly too. Don't worry about your win-loss record, focus instead on improving your skills.
This is not to say that you can't regularly win blood games. You just have to know how. The simple odds of you against the world mean that you will not win bloods as often as you would ally or grudge games, but there are a small handfull of blood specialists who will win 1/2 to 2/3 of the time (infinately more impressive to me than the 80-85 percent that marks the great players in ally and grudge games.)
The most common misconception about blood games is that they are absolute free for alls. In one respect the are since there is no diplomatic status besides war, but that is not a good winning strategy. Those who win regularly know that you have to break bloods down into a series of 1-on-1 matchups. Once you have won your face-off you then have the added resources to attack your neighbor, who will then have to fight on multiple fronts. You can then continue building like this until you nuke them all.
The typical blood player is nuked because he loses focus by having fronts on all sides. They see that, for example, a neighboring empire is busy on his other front and leaves his rear planets open to an easy nuke, so they move in and nuke the planet. Avoid this at all costs!! If you nuke that planet then your neighbor's economy suffers. This, then, will likely lead to his ultimate defeat by the empire he is fighting. That emp will then be able to take all of your neighbor's systems and come after you while you are still fighting on your other front.
Remember the oldest of diplomatic maxims...the enemy of my enemy is my friend. While there is no formal diplomacy, you should try to work out informal, and even unspoken, agreements with those around you. Ship and/or planet names can carry semi-private diplomatic messages to get your point across, but often just the simple and purposeful lack of exploration into the neighbor's territory is enough to make him reaize your intentions.
Just as there is a standard of behavior for team games, so is there an accepted ettiquette for blood games. While it was not included in the original Guide to Stellar Crisis Etiquette, the spirit of those guidelines has been extended to bloods and codified in the Blood Game Etiquette page.