How do I go about making an app for iphone/ipad etc

I have an idea I would like to make into an app. I just dont know where to start and how much it would cost to get one designed and made up from scratch. Can anyone help me with this? Sorry Im not very technology savvy. Also any helpful advice to make it successful and does anyone know if I can create one myself from an app template and how I go about this and any recommendations? Also is there good money to be made with a good app? TIA