Your best bet is to import your character from Origins. I'm not sure if it's possible to start with the Orlesian Warden and reach rank 30, but I do know that giving yourself the best headstart possible can't be a bad thing. The good news about leveling up is that it's much easier. Everything is worth more experience points. Kills that you got about 20-30 points for in Origins get you about 70-80 in Awakening. Along with completing the story, do as many sidequests as you can for extra XP. There are plenty to be found in Amaranthine.