How much single-sign (static) charge is storable in a reasonable mass?
The best I know is the tecnique used in supercaps: you let a thin layer of oxide grow between two metals. 

As the capacity is reverse-proportional to the distance of the two metals, this gives you a great value for the charge over voltage ratio... too bad this reduces the maximum voltage sustainable for the supercap.

On the other side we have Van der Graaf machines, that can store hundreds of kilovolts in the metallic end, but have a very low capacitance (so very low charge).

That said you should give us some more information about your design to be able to understand what are your requirements: the currents you need in the wires, how that currents flow out of the capacitors, etc.