Unfortunately, you really need a separate gun for each. A 20 ga which would be tolerable for kick, may be a bit light for turkeys and just ok for deer using slugs. Savage made combination guns, rifle on top of a shotgun. Some states allow the use of these. This is not a easy fix. Most of us were in your position as youngsters and you will find a gun to meet your immediate needs. Just think on it and don't be in a hurry to buy something. I started with a 16 ga remington shotgun, this was a good compromise at the time I was 14.