I can’t get one decent shave out of the cheap ones, I’ve tried.
https://www.google.com/search?q=razor+blade+sharpening+block+milk+glass&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiZneHH1snRAhUrqFQKHUoLBVwQ_AUICSgC&biw=1581&bih=726#tbm=isch&q=razor+blade+sharpener&imgrc=yblp4RIjgXgyAM%3A
I buy the BIC disposables and they work pretty good and are cheap.
https://www.walmart.com/search/?query=Razor%20Blade%20Sharpener&u1=&oid=223073.1&wmlspartner=TQiP6m79tRs&sourceid=33153145112848665315&affillinktype=10&veh=aff