Get the most out of Banner of Command!
It is quite an uncommon item, but when it's used a lot of people complain how underwhelming it is. There are actually a couple of ways to get your gold's worth here, and knowing when to buy it and use the active is VERY nice when you have it down.
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If the enemy has heavy AP waveclear, or heavy magic damage in general that is the perfect situation to buy it. Upgrading a minion renders it IMMUNE to magic damage along with making it generally harder to kill.
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Promote a caster minion for maximum pushing and gold generation. It will live way, way longer and isn't prioritized like melees. With the huge AD bonus it gets it becomes way more profitable than melee or tank minions, who attract attention from turrets and other minions and die before proving their worth.
That's about it. I am not too specific, but when I build it I usually do on a tank who can distract champions enough to let a wave do its pushing, usually Taric or Leona. Thanks for reading.