I want to adopt a new dog from a shelter but dont know what kind
That is great!  I have wonderful chocolate lab,   do you have a backyard?
I live out in the country so I have lots of open area around my house.  I had a black lab who just showed up at my house years ago and never left.  
Perfect. Would you are looking for a companion for your dog? do you want a small or a large dog? 
My lab died last year.  Dogs long association with humans changed their diet to be able to eat more carbs than other similar species?  My lab certainly ate anything!