I want to ask where should we use pearls in royal revolt 2

Troops, towers and equipment.

Base on level, I think troops are important and barricades as soon as you can. When you get legendary equipment invest in them to turn them ruby. Pearls are important everywhere in the game.

 Concentrate on using your pearls on forging your spells and troops to start with,  Barricades and towers later. 

yes first use pearls for the forging of spells and units ,remaining all are later