Think of power as electricity, axles as power-lines, gears as power routing stations and all dwarven buildings requiring power as electrical devices. I didn't understand what your problem was specifically, so I'll give a bunch of general solutions, including some problems I had when I first started playing.
Generating Power
First, water wheels are the way to go.
Windmills can power single structures or help you in a fix, but thats about as far as their utility goes, especially if you are in a low-wind/windless map.
You need to be able to generate power to use it. The best way is to make a waterwheel on a brook (you need to channel the tiles on which you want to build the wheel on first). The wiki talks about Perpetual Motion Devices, but these generate little power, roughly 100-200 power in the wiki designs, whereas a single "power station" encased in walls built on a brook can have much more, dependant only on how big you want to make it (mine usually have 1K, with me building more stations as they are needed).
Waterwheels will generate full power if one tile of water underneath them is "moving". In a brook all tiles of water are "moving". Water is moving if its symbol alternates between ~ and the double tilde (two ~ in one symbol).
Delivering Power
First, power doesn't move. If something is connected to another system that has power there are no need for any logistics about mechanical contradictions, they just need to connect and poof, everything in the now connected system has the power of both systems.
Devices (and power generators (except windmill!)) function exactly like gear assemblies in the way they route power. They, like gear assemblies can take/receive power from any orthogonal direction, including from higher up z-levels. They can have an unlimited amount of connections (well, limited by how many squares are free in orthogonal directions, obviously). If there is not enough power in the system to fuel its needs, even if 1 power unit is missing, nothing in the system will work.
Devices (and power lines etc.) don't need any support to function, they can be built "hanging" if they are connected to another unit that has something to do with power, although your dwarves will need a way to access it to build it.
About Screw Pumps
Screw pumps take fluids from the level below them and move it to the level on which they are on, with incredible speeds. A single screw pump can (remember, they function just like gears!) move power to any adjacent screw pump (if you hollow out the ceiling/floor you can also build screw pumps "hanging", supported by the pump below/above them! Only one square would be needed to transfer power though.)
Hope that helped