I find a backstory helps me play a character other than myself and make character consistent decisions. That said, I don't think level 1 needs much backstory, unless they've been diminished in power like Gale.

Guy (placeholder name)
- Human noble raised in Baldur's Gate.
- Squired as Companion Knight in Elturel.
- Talent wasted and ambition dulled by years at Fort Tamal.
- Eventually left posting without accomplishment.
- Returning to Baldur's Gate, heard rumours of Elturel's descent, resolved to return to help.
- Like many others, was abducted by mindflayers.

Personality: Looks the part, always well groomed, however his cocky one-liners are stupid as often as cool.
Ideal: Heroism, wants to be viewed a hero.
Bonds: Nobles of Baldur's Gate, knights of Elturel, commonfolk in general.
Flaw: Ashamed to return home without accomplishments, so easily convinced to undertake 'quests'.