That depends on you! GDs are actually not bad apartment dogs despite their size. They are (generally) pretty low energy for the majority of the day --lazing around on the furniture-- and then they are wild pups when it's play time. As long as you have a good exercise outlet, the apartment isn't really the problem (assuming you are, and always will be, committed to finding an apartment that will allow such a large dog).
With a GD as a first dog, you will have to be VERY committed to doing your research. Large dogs have a lot of health concerns and need specialized feeding and care. They are also much more expensive in general. Not just food, but flea meds and heartworm meds and any other medication. Also, they often do not live as long as smaller breeds.
I would contact GD rescues and get an idea of what to expect. Breed rescues are very helpful and, more importantly, HONEST when it comes to explaining the benefits and drawbacks of their breed. They genuinely want to place the pup in a forever home and it's not about the money with them.
I would also recommend looking for an adult dog to start off. Puppies, especially large breed puppies, are so much harder and not for a novice dog owner. An adult dog will likely come to you housetrained and socialized (one from a rescue anyway). You will know whether they will be high, medium, or low energy and can pick one that suits your lifestyle. Many breed rescues will work hard to match you with a suitable dog. Not to mention, you will be saving a dog's life! Even if a dog in a breed rescue is already safe, by adopting a dog from them you are allowing them the resources to rescue another dog in need!
Check out this site: www.bigdogsporch.com
It's a forum specifically for people with large breed dogs. There are several very nice, helpful GD owners on there who would love to give you advice! Not to mention, there are wonderful photos! Two in particular have gorgeous Danes.