These Mr. Control single speed conversion kits will allow you to turn any geared bike (using deraillieurs) into a single speed. The sprocket will fit any 7 speed or 8/9/10/11 speed shimano type MTB freehub body (except the WH-6600 and WH7800 and FH 7800 tall splined freehub shimano road wheels produced for a few short years). The sprocket is made of steel and have tall teeth preventing derailment. I run these myself and found them faultless. Spacers and lockring are included.
These sporckets kits can be used on 11 speed road hubs too but will require an additional 1.85mm spacer.
11 speed MTB freehubs for shimano have the same length as a 10 speed freehub so no worries here.
The sprocket suits 8 speed chains but narrower 9 or 10 speed chains will work too. I have runs 1/8" chains on this with no issue as well.
So if yo want a cheap simple drivetrain this is the best way to get it.