Build a model in pieces for a kit. What do I need to supply?

I want to have a design printed and one prototype and if OK make perhaps ten or more.  How do I form all of the parts to do this?  Do I put them on a sprue as compact as possible or lay them on a flat surface.  I have two FDM printers and can not get the resolution I need from them.  Also, what material do you suggest for printing the parts?

I'm thinking a nylon type material would be best.

I have the design of the individual pieces available and can send the as OBJ or STL files.  Can you send me a picture of an example?

This would be a model about 6 inches long (the longest dimension) after all of the parts are assembled.  Below is a screen shot of the entire model.  Some of the smaller parts may not be printable and I can make them out of some metal.