Too many factors for a forum to help you. There are people full timing with three dogs in a 25' Class C. There are two adults, no pets, full timing in a 45' and towing a 20' workshop/car hauler and they're still isn't enough room.
Your budget will dictate what size and year coach you get.
We had a 36' DP for almost ten years and it served us well. When we went new, there were things I wanted, like a side radiator, tag axle and engine brake. The smallest coach we could find with these attributes was our Newmar. If I were to go full time, I would buy a 45' DP that had plenty of outside storage and enough interior space to give us some separation when needed.