^^ Awesome dogs when trained properly, seriously loyal and very intelligent, but they need firm training.
Edit: Referring to the Doberman.
I have two fab rescue Saluki x Greyhound lurchers. They're incredibly good tempered, very friendly and very gentle - something I've experienced in all sighthounds I've had anything to do with.
If I were you, for a first dog I'd definitely go for something Greyhound-ish as they really aren't at all demanding, and are very easy to have around the house - my two would sleep all day if I let them!
Just make sure that whatever you get will fit in with your lifestyle - some breeds make dreadful pets for some people whilst being another person's perfect pet - this applies particularly to those dogs bred to work, such as Collies, Spaniels and even Labs.
Whatever you get, I'd definitely, definitely go for a rescue - I was a bit wary of rescues before I got my two - dreading that something awful might surface when we got them home, but the worst we've had is a bit of separation anxiety from one, which is now getting much better and a fear of strange dogs in the other (understandable, as she has scars which would indicate being kept with another dog which was highly aggresive towards her) which, again, is now vastly improved. Otherwise they're aazing, and take everything into their stride - including my five year old nephew trying to ride them!
All dogs need proper training and socialising so they are friendly, happy and will not cause you any problems.
As a first time owner I would probably advise you to stay away from breeds like rottwielers, dobermans and staffeys as they have a natural aggressiveness in them.
I would say something like a golden retriever makes perfect family dogs or solo dogs, and they have a happy temper.