Here's a professional bike mechanic's take on cheap cone and ball-bearing wheel hubs.
Before you put that wheel in service, get the proper tools to do a wheel bearing overhaul, ( adjustable wrenches, cone wrenches, freewheel or freehub cog remover..) and disassemble the hub, remove the caged ball bearings, clean all the bearing surfaces sparkily clean of the OEM grease in mineral spirits, then pop the bearings out of their retainers and buy enough additional 1/4" ball bearings to load both sides of the hub with loose ball bearings. ( most likely about 9 per side..)
If running a rag joint drive sprocket, I'd replace the quick-release axle with a BMX or MTB equivalent nutted axle, preferably of Cro-Moly like Theon recommends. I would check your rear axle drop-outs for alignment just to be safe.
Dry the hub of any traces of solvent, then pack both the cups of the hub with high quality axle or outboard drive grease, and install the ball-bearings loose and then install the axle/cones and carefully adjust the cones/locknuts to a slightly light preload so that there is a trace of friction while turning, but not so tight it feels stiff or rough.
Having some spots with a tiny amount of free play won't hurt, these aren't Campy quality hubs, for that matter they 're not even Atom or Mallaird quality, but they will last with proper adjustment and frequent servicing.
They weren't really designed to handle more than one human power in normal use.
Which is true of most bicycles in motorized bike use.
Caveat Emptor!