Putting together 3-4 guides, and changing things that people suggested... I came up with this skill build:
Lv.3 - Aimed Shot: +1 Power
Lv.5 - Power Shot: +1 Power
Lv.7 - Power Shot: +1 Power
Lv.9 - Power Shot: +1 Power
Lv.11 - Fury Impact: +1 SP Reduction
Lv.13 - Fury Impact: +1 SP Reduction
Lv.15 - Bone Shot: +1 SP Reduction
Lv.17 - Bone Shot: +1 Duration OR SP Reduction
Lv.19 - Power Shot: +1 SP Reduction
Lv.21 - Power Shot: +1 SP Reduction
Lv.23 - Aimed Shot: +1 Power
Lv.25 - Aimed Shot: +1 SP Reduction
Lv.27 - Aimed Shot: +1 SP Reduction
Lv.29 - Aimed Shot: +1 Power
Lv.31 - Fury Impact: +1 SP Reduction
Lv.33 - Bone Shot: +1 SP Reduction
Lv.35 - Fury Impact: +1 SP Reduction
Lv.37 - Bone Shot: 1 SP Reduction
Lv.39 - Fury Impact: +1 SP Reduction
Lv.41 - Bone Shot: +1 SP Reduction
Tell me what you think 
And please, if you have ANY build suggestion - tell me here!