I would definitely second (or third) the opinion to plant it in the ground to let it thicken up a bit. Or, if that's not possible, plant it in a larger pot and let it grow grow grow.
If the roots are terrible, beyond being salvageable, then you can try using the hole-in-the-tile technique for developping (almost) flawless nebari.
Here is the thread explaining the technique.
-Audric