Got Fire Emblem Awakening! (Have some questions)

[domflo]

Depends. Most of them are only interesting if you've played other Fire Emblem games (Champions, Lost Bloodlines, Smash and Rogues). I'd go for the "The Future Past" pack, because it adds a bit of story if I could only choose one pack. The "Golden" pack (as I think it's called) is basically providing you with easy money and experience, but some say that it's necessary should you want to beat the game on Lunatic(+). The Scramble pack is interesting as well, since it provides a lot of conversations between the characters in the game, adding depth to them. The Challenge pack and the Apetheosis DLC are interesting if you're, well, up for a challenge. They are quite hard actually.
So yeah, each DLC has it's worth, and in the end it depends on how much you like the game and how much you are into the series. If you're a series newcomer, you can probably skip the first batch of DLC I mentioned, and Challenge and Apotheosis might be a bit overkill as well. Again, the Golden pack is only interesting for easy grinding, so you can probably skip that too, which leaves us with the Future Past and the Scramble pack. They're probably the ones I would recommend the most, but again, only if you want to learn more about the characters in the game. If you're not interested in that, you can skip DLC altogether.

Edit: Yes, DLC adds maps and characters. The characters have no actual character though and are only additional units to deploy. Maps are often based off of maps out of older Fire Emblem games. If you just want more to play, you can take any DLC really.

The character-unlock DLC (the first ones I mentioned) add dialogue with characters from past Fire Emblem games, but again, that's only interesting if you know about these characters to begin with.