It really depends on the faction, the type of soldier, and how often you play those. I love Droid Swarms and Poggle Bombs (Geonosian Drone's, fueled with Self-Destruct 20 from Poggle the Lesser, a v-set 1 piece). So, I keep 20+ Drones/Battle Droids on hand. Sometimes I play standard clone troopers, I have about 8. But, like Sith Troopers, I usually play Sith Guards or Operatives instead, so I only have a couple, but several Ops and Guards. So it depends on what you will use.
That's just my opinion, hope it helps
