Hints: Puzzle of Dragons

Getting started:
In each board, you have to use some subset of the active skills to make a board with which it’s possible to satisfy the leader skills of both leaders. The “After using your skills, there should be a straight path available. Start at the beginning and move right along to the end.” message means that after using the active skills correctly, the resulting move to make the combos needed for the leader skills is always dragging an orb in the left column horizontally to the right column.
Stuck on extraction:
The number of blanks above each puzzle is equal to the number of skills you use in solving it. It’s also equal to something else (in particular, what about the grids haven’t you used yet?).