you're gonna need an exhaust on there to get any carb set up right. and that mess of wires where the headlight should be, ugh. good luck.
I've seen a hobbit carb on a nu50 before, that $20 clone may work if you open up the mounting holes toward the center, hobbit intake studs are farther apart. it will be jetted too rich for your bike, but it might not matter of you use a high flow filter like pictured with the revo carb, or some people just use a scrap of oiled pantyhose over the intake on the carb. it will be loud without an airbox, if that matters to you.
just to confirm, is the stock intake still there, just missing the carb?
i think the nx50 uses vacuum to open & close the petcock, not exactly sure how that works. that will cause some issues without the stock setup.
I have a nu50m which has a very similar motor, but there are some differences. I'd suggest searching this site, all forums, all dates, and reading all you can about the nx50 for more details.
here's the nu50 manual , it should help get you going.