What is the best thing to put on your skin to stop it from peeling and to get the redness out from a sunburn?

Cold milk. To reduce the discomfort cold milk compresses will soothe and the skin and calm the burning sensation. A non steroidal such as allege, Motrin or Aspirin will decrease the inflammation.Aloe can be added to the regimen. A dermatologistcanpres ribe a steroid cream to cut down on the redness .
Nothing. You lose the top layer of your skin every 7 days anyway and with sunburn the damaged skin has to come off. The redness has to heal over time. You can soothe the skin and maybe speed it up by a day or two by applying moisturising lotion containing aloe vera and avoiding sun exposure till it is healed.
Simple Treatment. Sunburn is response of the tissues to injury from solar radiation. It is simply inflammation which means increase blood flow to the area to promote healing. Do not use ice as this can injure already injured skin. Cool water soaks can help as can taking anti-inflammation medicines like Motrin or advil (ibuprofen). Avoid any further damage as this can cause scarring . Good skin cream applied daily/gently helps.