That depends on your own condition. If you have the same prescription in both eyes, then you can wear over the counter reading glasses with no problem because OTC reading glasses always have the same prescription in both lenses.
If you have different prescription in both eyes, you'd better not use OTC reading glasses because they won't fit your well. If you often wear these reading glasses, they may make you uncomfortable and ruin your eyesight. I think you should go to an optical store to get prescription reading glasses.
Non prescription reading glasses are made with the same power in both lenses. They are suitable for people whose eyes have the same power in both eyes. However, most people have different unique prescription. If you have your own unique prescription, non prescription reading glasses will make you feel uncomfortable and actually cause problems instead of helping to correct vision. Some people will even have sore eyes and dizziness when they wear non prescription reading glasses for a long time. So it is better and more saft to wear prescription one.