I tip from my wall first. Those are my most loyal neighbors. If get around to everyone it is a bonus. I try to keep 30-35 on each game (2 bs and 2 rs). Just enough to build stuff and receive max gifts each day.
Before I took an 18 month break from the game I had so many neighbors, it just burned me out. Now I delete the demanding neighbors, I can't keep up with them anymore.