Since you use only one rear cassette cog, you should shift to it and align it to the top jockey wheel of the rear derailleur. The derailleur has a cable adjuster for it. It should run without any noise.
If that cog is not in the middle of the cassette, but on the left or right side, it will be noisier because the chain runs at an angle - the chainline is not perfect. You can get a different chain ring for the crankset.

You can lube the chain.