I can give some ideas about skill tree. But let me think of it. I have creative mind. 
Trust me, I used to play with my own book(drawing book) sketching some naruto game.
If you ask me, I can think of a skill tree and skills, just tell me how the game will be like(RPG, turn-base....etc.)
Trust me, I used to play with my own book(drawing book) sketching some naruto game.
If you ask me, I can think of a skill tree and skills, just tell me how the game will be like(RPG, turn-base....etc.)