Don't use war money to buy war items, use it only to buy boosters.

Why?

War money is a scarce commodity and although there are tricks to get more of it, they are not tricks that will make you rich from this loot. So use it very sparingly and don't spend it on goods that can be obtained by other means.

How should it be done?

Use the war money to buy battle boosters (jackpots, duds, vampires, etc.); and get the war items through the shipments enabled to get them. This will be the most efficient way to avoid wasting your War money (purples).