Whats the best breed, for a laid back and quiet pony?

I don't think I have met a laid back, quiet, nice natured, not pony. I am pretty sure ponies are these things by nature. It would be better for you to research specific bloodlines in breeds to find what you are looking for than breeds themselves. For example a thoroughbred by a stud known for producing quiet amateur friendly horses is going to be entirely deferent from a thoroughbred by a stud known for producing hot, athletic pro rides. These would both be the same breed but not at all the same temperament. In general I would avoid arabians and welshes for what you want because the majority I have met had a lot of get up and go and were on the nervous side. Keep in mind there are always exceptions.