I'm asking here because I don't want spoilers. Just yes or no answers. In case of "yes", please, tell me what DLC should I play and in what order.
Mass Effect 1's "Bring Down the Sky" has an effect in Mass Effect 2 and 3. The other available DLC, "Pinnacle Station", does not.
You've asked to avoid spoilers, so I'll simply say that the default canon is that Bring Down the Sky ends with the Renegade ending. If you play it personally, you can alter this.