You should have more than one hat line, and be sure to pitch the ending as a way to make people stay. Consider having something to make the first group stop, and be sure to make the transitions as smooth as possible, and as tightly scripted as you can make them. Transitions are the weakest part of the set, so they have to be extra good to keep people from leaving. Make sure you have something going on.
Get some resources specific to busking.
Have posted my routine recently. Pm me if I can be of more help.