One Stars generally just get an increase in their abilities as it is I believe two stars is when things start to get funky so to speak. For an archer I'd think accuracy and precision would take more over agility. Speed definitely is valid of course as well.

For two stars I'd personally go with something that would either let me shoot better, give me elemental effects or more physical types of punch or versatility, shoot more arrows at a time, the ability to shoot with more accuracy with some sort of scope that goes over the eye and or the ability to shoot from different surfaces. Really however that's just me if you want to build your character that way so be it I just don't think it would be as effective as it could be as you'd need to deal with sliding on the walls and unsteady areas and being quick rather than hitting the target effectively. Unless your going for arrow spam.