I myself mostly level them up to lvl 7 or 8, depending on how I feel like. Currently my lvl 17 War glad has her weapon-skill at lvl 9 and I think I'm gonna stick to that till about lvl 20. But that's a war.... For a Rage (just got a new Rage glad, also my first) I think I'm gonna lvl it like this:
Weapon - 7
Brute Force - 3
Then
Weapon - 8
Brute Force -5
Sunder Armor - 5
And then I'll just see :P