i learned a change up next. but most coaches teach the change up or drop next. it all depends i would try either of them! hope i helped!

After fastpitch, and pitching inside/outside, I think change up

After locating fastball well, an offspeed or a change up hitting location.

most common order would be the fast ball, change up, drop ball, then the rise ball..

hope this helped

for more tips and drills check this:
http://www.softballperformance.com/softball-tips/softball-pitching-tips.html

INSIDE CONER/OUTSIDE CONER, CHANGE UP